From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 511FFC001DB for ; Mon, 14 Aug 2023 14:30:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231184AbjHNO3o (ORCPT ); Mon, 14 Aug 2023 10:29:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232492AbjHNO3T (ORCPT ); Mon, 14 Aug 2023 10:29:19 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0F3D618E for ; Mon, 14 Aug 2023 07:29:16 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 87A9563656 for ; Mon, 14 Aug 2023 14:29:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92A14C433C7; Mon, 14 Aug 2023 14:29:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692023354; bh=WnsO4PSfA1dxyC1mNMIBf0lMmWesMYzxObMkZwK/xiU=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=fsMTR4GSk7Bt6y0F9E0D7mRMtKFzBDUGGjWdkftN2D23goLJ8rPXLfFSMiyhESNRw xNZERsOB4LbRp5tC3N74xvlRDh/9INpamNhIEnKL2JwtKbsgqDhPSm7UcwxIbwzNHU lrwvn1Z5MCBN9D6RjYMRYfCNo0c8sxtqjNdS3m53GSN4aQLsUO2OD3e4HroFPvAtRi DIbxP6RlodjJBercmCr2wPq25/iUaPVkTocpkvj8/Q+ExsEQ64SDtBFq38229JFGSY Lb1irAuS6n6diirByu4p7QBfV/byFf806huBZdwFIC35KqErm9EBvbVNgi46BQdgHs 6QEyG2N5wP7HA== From: =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= To: Puranjay Mohan Cc: paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, pulehui@huawei.com, conor.dooley@microchip.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, kpsingh@kernel.org, bpf@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH bpf-next 0/2] bpf, riscv: use BPF prog pack allocator in BPF JIT In-Reply-To: References: <20230720154941.1504-1-puranjay12@gmail.com> <87pm3qt2c8.fsf@all.your.base.are.belong.to.us> <87v8dhgb4u.fsf@all.your.base.are.belong.to.us> Date: Mon, 14 Aug 2023 16:29:12 +0200 Message-ID: <87zg2telzb.fsf@all.your.base.are.belong.to.us> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Puranjay Mohan writes: > On Mon, Aug 14, 2023 at 12:40=E2=80=AFPM Bj=C3=B6rn T=C3=B6pel wrote: >> >> Bj=C3=B6rn T=C3=B6pel writes: >> >> > Puranjay Mohan writes: >> > >> >> BPF programs currently consume a page each on RISCV. For systems with= many BPF >> >> programs, this adds significant pressure to instruction TLB. High iTL= B pressure >> >> usually causes slow down for the whole system. >> >> >> >> Song Liu introduced the BPF prog pack allocator[1] to mitigate the ab= ove issue. >> >> It packs multiple BPF programs into a single huge page. It is current= ly only >> >> enabled for the x86_64 BPF JIT. >> >> >> >> I enabled this allocator on the ARM64 BPF JIT[2]. It is being reviewe= d now. >> >> >> >> This patch series enables the BPF prog pack allocator for the RISCV B= PF JIT. >> >> This series needs a patch[3] from the ARM64 series to work. >> >> >> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D >> >> Performance Analysis of prog pack allocator on RISCV64 >> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D >> >> >> >> Test setup: >> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >> >> >> >> Host machine: Debian GNU/Linux 11 (bullseye) >> >> Qemu Version: QEMU emulator version 8.0.3 (Debian 1:8.0.3+dfsg-1) >> >> u-boot-qemu Version: 2023.07+dfsg-1 >> >> opensbi Version: 1.3-1 >> >> >> >> To test the performance of the BPF prog pack allocator on RV, a stres= ser >> >> tool[4] linked below was built. This tool loads 8 BPF programs on the= system and >> >> triggers 5 of them in an infinite loop by doing system calls. >> >> >> >> The runner script starts 20 instances of the above which loads 8*20= =3D160 BPF >> >> programs on the system, 5*20=3D100 of which are being constantly trig= gered. >> >> The script is passed a command which would be run in the above enviro= nment. >> >> >> >> The script was run with following perf command: >> >> ./run.sh "perf stat -a \ >> >> -e iTLB-load-misses \ >> >> -e dTLB-load-misses \ >> >> -e dTLB-store-misses \ >> >> -e instructions \ >> >> --timeout 60000" >> >> >> >> The output of the above command is discussed below before and after e= nabling the >> >> BPF prog pack allocator. >> >> >> >> The tests were run on qemu-system-riscv64 with 8 cpus, 16G memory. Th= e rootfs >> >> was created using Bjorn's riscv-cross-builder[5] docker container lin= ked below. >> >> >> >> Results >> >> =3D=3D=3D=3D=3D=3D=3D >> >> >> >> Before enabling prog pack allocator: >> >> ------------------------------------ >> >> >> >> Performance counter stats for 'system wide': >> >> >> >> 4939048 iTLB-load-misses >> >> 5468689 dTLB-load-misses >> >> 465234 dTLB-store-misses >> >> 1441082097998 instructions >> >> >> >> 60.045791200 seconds time elapsed >> >> >> >> After enabling prog pack allocator: >> >> ----------------------------------- >> >> >> >> Performance counter stats for 'system wide': >> >> >> >> 3430035 iTLB-load-misses >> >> 5008745 dTLB-load-misses >> >> 409944 dTLB-store-misses >> >> 1441535637988 instructions >> >> >> >> 60.046296600 seconds time elapsed >> >> >> >> Improvements in metrics >> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >> >> >> >> It was expected that the iTLB-load-misses would decrease as now a sin= gle huge >> >> page is used to keep all the BPF programs compared to a single page f= or each >> >> program earlier. >> >> >> >> -------------------------------------------- >> >> The improvement in iTLB-load-misses: -30.5 % >> >> -------------------------------------------- >> >> >> >> I repeated this expriment more than 100 times in different setups and= the >> >> improvement was always greater than 30%. >> >> >> >> This patch series is boot tested on the Starfive VisionFive 2 board[6= ]. >> >> The performance analysis was not done on the board because it doesn't >> >> expose iTLB-load-misses, etc. The stresser program was run on the boa= rd to test >> >> the loading and unloading of BPF programs >> >> >> >> [1] https://lore.kernel.org/bpf/20220204185742.271030-1-song@kernel.o= rg/ >> >> [2] https://lore.kernel.org/all/20230626085811.3192402-1-puranjay12@g= mail.com/ >> >> [3] https://lore.kernel.org/all/20230626085811.3192402-2-puranjay12@g= mail.com/ >> >> [4] https://github.com/puranjaymohan/BPF-Allocator-Bench >> >> [5] https://github.com/bjoto/riscv-cross-builder >> >> [6] https://www.starfivetech.com/en/site/boards >> >> >> >> Puranjay Mohan (2): >> >> riscv: Extend patch_text_nosync() for multiple pages >> >> bpf, riscv: use prog pack allocator in the BPF JIT >> > >> > I get a hang for "test_tag", but it's not directly related to your >> > series, but rather "remote fence.i". >> > >> > | rcu: INFO: rcu_sched detected stalls on CPUs/tasks: >> > | rcu: 0-....: (1400 ticks this GP) idle=3Dd5e4/1/0x40000000000= 00000 softirq=3D5542/5542 fqs=3D1862 >> > | rcu: (detected by 1, t=3D5252 jiffies, g=3D10253, q=3D195 ncp= us=3D4) >> > | Task dump for CPU 0: >> > | task:kworker/0:5 state:R running task stack:0 pid:319= ppid:2 flags:0x00000008 >> > | Workqueue: events bpf_prog_free_deferred >> > | Call Trace: >> > | [] __schedule+0x2d0/0x940 >> > | watchdog: BUG: soft lockup - CPU#0 stuck for 21s! [kworker/0:5:319] >> > | Modules linked in: nls_iso8859_1 drm fuse i2c_core drm_panel_orien= tation_quirks backlight dm_mod configfs ip_tables x_tables >> > | CPU: 0 PID: 319 Comm: kworker/0:5 Not tainted 6.5.0-rc5 #1 >> > | Hardware name: riscv-virtio,qemu (DT) >> > | Workqueue: events bpf_prog_free_deferred >> > | epc : __sbi_rfence_v02_call.isra.0+0x74/0x11a >> > | ra : __sbi_rfence_v02+0xda/0x1a4 >> > | epc : ffffffff8000ab4c ra : ffffffff8000accc sp : ff20000001c9bbd0 >> > | gp : ffffffff82078c48 tp : ff600000888e6a40 t0 : ff20000001c9bd44 >> > | t1 : 0000000000000000 t2 : 0000000000000040 s0 : ff20000001c9bbf0 >> > | s1 : 0000000000000010 a0 : 0000000000000000 a1 : 0000000000000000 >> > | a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000 >> > | a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000052464e43 >> > | s2 : 000000000000ffff s3 : 00000000ffffffff s4 : ffffffff81667528 >> > | s5 : 0000000000000000 s6 : 0000000000000000 s7 : 0000000000000000 >> > | s8 : 0000000000000001 s9 : 0000000000000003 s10: 0000000000000040 >> > | s11: ffffffff8207d240 t3 : 000000000000000f t4 : 000000000000002a >> > | t5 : ff600000872df140 t6 : ffffffff81e26828 >> > | status: 0000000200000120 badaddr: 0000000000000000 cause: 80000000= 00000005 >> > | [] __sbi_rfence_v02_call.isra.0+0x74/0x11a >> > | [] __sbi_rfence_v02+0xda/0x1a4 >> > | [] sbi_remote_fence_i+0x1e/0x26 >> > | [] flush_icache_all+0x1a/0x48 >> > | [] patch_text_nosync+0x6c/0x8c >> > | [] bpf_arch_text_invalidate+0x62/0xac >> > | [] bpf_prog_pack_free+0x9c/0x1b2 >> > | [] bpf_jit_binary_pack_free+0x20/0x4a >> > | [] bpf_jit_free+0x56/0x9e >> > | [] bpf_prog_free_deferred+0x15a/0x182 >> > | [] process_one_work+0x1b6/0x3d6 >> > | [] worker_thread+0x84/0x378 >> > | [] kthread+0xe8/0x108 >> > | [] ret_from_fork+0xe/0x20 >> > >> > I'm digging into that now, and I would appreciate if you could run the >> > test_tag on VF2 or similar (I'm missing that HW). >> > >> > It seems like we're hitting a bug with this series, so let's try to >> > figure out where the problems is, prior merging it. >> >> Hmm, it looks like the bpf_arch_text_invalidate() implementation is a >> bit problematic: >> >> +int bpf_arch_text_invalidate(void *dst, size_t len) >> +{ >> + __le32 *ptr; >> + int ret =3D 0; >> + u32 inval =3D 0; >> + >> + for (ptr =3D dst; ret =3D=3D 0 && len >=3D sizeof(u32); len -=3D= sizeof(u32)) { >> + mutex_lock(&text_mutex); >> + ret =3D patch_text_nosync(ptr++, &inval, sizeof(u32)); >> + mutex_unlock(&text_mutex); >> + } >> + >> + return ret; >> +} >> >> Each patch_text_nosync() is a remote fence.i, and for a big "len", we'll >> be flooded with remote fences. > > I understand this now, thanks for debugging this. > > We are calling patch_text_nosync() for each word (u32) which calls > flush_icache_range() and therefore "fence.i" is inserted after every > word. But more importantly, it does a remote fence.i (which is an IPI to all cores). > I still don't fully understand how it causes this bug because I lack > the prerequisite > knowledge about test_tag and what the failing test is doing. The test_tag is part of kselftest/bpf: tools/testing/selftests/bpf/test_tag.c TL;DR: it generates a bunch of programs, where some have a length of, e.g, 41024. bpf_arch_text_invalidate() does ~10k of remote fences in that case. > But to solve this issue we would need a function like the x86 > text_poke_set() that will only > insert a single "fence.i" after setting the whole memory area. This > can be done by > implementing a wrapper around patch_insn_write() which would set the memo= ry area > and at the end call flush_icache_range(). > > Something like: > > void *text_set_nosync(void *dst, int c, size_t len) > { > __le32 *ptr; > int ret =3D 0; > > for (ptr =3D dst; ret =3D=3D 0 && len >=3D sizeof(u32); len -=3D = sizeof(u32)) { > ret =3D patch_insn_write(ptr++, &c, sizeof(u32)); > } > if(!ret) > flush_icache_range((uintptr_t) dst, (uintptr_t) dst + len= ); > > return ret; > } > > Let me know if this looks correct or we need more details here. > I will then send v2 with this implemented as a separate patch. Can't we do better here? Perhaps a similar pattern like the 2 page fill? Otherwise we'll have a bunch of fixmap updates as well. I'd keep the patch_ prefix in the name for consistency. Please measure the runtime of test_tag pre/after the change. I don't know if your arm64 work has similar problems? Bj=C3=B6rn