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Fri, 23 Oct 2026 00:51:47 -0700 (PDT) Received: from gmail.com ([185.220.236.117]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ea7b368c90sm7208265ad.29.2026.10.23.00.51.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Oct 2026 00:51:47 -0700 (PDT) From: Jia Jia To: netdev@vger.kernel.org Cc: stefanha@redhat.com, sgarzare@redhat.com, bobbyeshleman@meta.com, mst@redhat.com, jasowangio@gmail.com, eperezma@redhat.com, xuanzhuo@linux.alibaba.com, davem@davemloft.net, edumazet@kernel.org, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, kvm@vger.kernel.org, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH net-next v5 0/5] vsock/virtio: reduce RX per-packet socket overhead Date: Fri, 23 Oct 2026 15:51:35 +0800 Message-Id: <20261023075140.9613-1-physicalmtea@gmail.com> X-Mailer: git-send-email 2.34.1 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This series reduces per-packet socket overhead in the virtio-vsock RX worker. Patch 1: separate socket lookup from locked packet processing. Patch 2: factor out the RX skb metadata-budget check. Patch 3: keep one socket lock across a bounded run of established STREAM/RW packets for the same native socket, and reuse the locked socket for later same-flow packets. Patch 4: coalesce default write-space notifications while that lock is held. Patch 5: defer the default readable callback until after the batch unlocks. Performance: Tested on a single-stream vsock connection (one Guest receiver thread on CPU0, virtio-vsock IRQ on Guest CPU1, fresh QEMU Guest per state, with 16 balanced AB/BA pairs per payload for each baseline/patchset comparison). The host uses vhost-vsock. For throughput, vsock_perf runs on the host as the sender, with a custom single-threaded Guest receiver pinned to Guest CPU0 using blocking recv(). The fixed-64K table uses a 64K buffer; the matched table uses the sender's request size. The virtio-vsock IRQ/RX worker is pinned to Guest CPU1. To normalize run times across payloads into a bounded, deterministic window and avoid long runs being skewed by host background noise or virtualization scheduling jitter, transfer sizes scale proportionally with the request size (64B/64M, 256B/256M, etc.), capped at 2G for 4K–64K. The custom receiver keeps the recv() size and count explicit; vsock_perf's receiver uses poll()+read(). Latency uses a custom user-space vsock ping-pong tool. The measurements below were collected for the RX batching series. This benchmark does not run vsock_perf on both ends. Instead, it uses vsock_perf as the sender on the host (vhost-vsock) side and a custom blocking recv() program without poll() on the Guest side, with the receiver thread pinned to Guest CPU0 (and the virtio-vsock RX worker pinned to Guest CPU1). Plain blocking recv() combined with strict core pinning gives audit-level determinism for tracing a single-threaded TID. With all patches applied: End-to-end RX throughput (64K Guest recv() size, SO_RCVLOWAT=1; Gbit/s): payload baseline RX PATCH RX throughput change (95% CI) (Gbit/s) (Gbit/s) 64B 0.1290 0.2489 +92.91% [+89.31%, +96.58%] 256B 0.5780 0.9727 +68.29% [+66.14%, +70.48%] 512B 1.1688 1.8316 +56.70% [+53.85%, +59.61%] 1K 2.3059 3.3377 +44.75% [+43.39%, +46.12%] 4K 3.8787 5.7310 +47.76% [+45.20%, +50.36%] 8K 4.5983 5.4575 +18.68% [+16.42%, +20.99%] 16K 5.0806 5.5615 +9.47% [ +8.05%, +10.90%] 64K 5.4842 5.6423 +2.88% [ +1.13%, +4.67%] Fixed-syscall stress test (receiver recv() size = sender write size; Gbit/s): payload baseline PATCH throughput change (95% CI) recv() RX RX (base/patch) (Gbit/s) (Gbit/s) 64B 0.1384 0.2532 +82.99% [+74.19%, +92.24%] 1048577/1048577 256B 0.4042 0.8983 +122.25% [+113.06%, +131.85%] 1048577/1048577 512B 0.8056 1.6035 +99.05% [+89.34%, +109.26%] 1048577/1048577 1K 1.6030 2.7158 +69.42% [+63.22%, +75.85%] 1048577/1048577 4K 3.0194 4.9586 +64.22% [+58.43%, +70.23%] 536799/525225 8K 3.8316 5.1255 +33.77% [+31.00%, +36.59%] 274864/263013 16K 4.5702 5.3808 +17.74% [+14.87%, +20.67%] 144958/131332 64K 5.4736 5.7118 +4.35% [ +2.79%, +5.94%] 49039/32938 Request-response latency (Ping-Pong RTT, 10,000 requests): payload baseline mean RTT (us) PATCH mean RTT (us) change (95% CI) 64B 224.148 224.151 +0.00% [-2.26%, +2.32%] 256B 222.037 224.499 +1.11% [-1.66%, +3.95%] 4K 225.982 227.026 +0.46% [-1.15%, +2.10%] Guest CPU1 aggregate cycles per received byte (fixed 64K receiver, with perf): Buffer size baseline cycles/B PATCH cycles/B cycles change (95% CI) 64B 65.282 57.843 -11.40% [-13.77%, -8.95%] 256B 14.710 13.813 -6.10% [ -7.89%, -4.28%] 512B 7.709 7.188 -6.75% [ -8.79%, -4.66%] 1K 4.075 3.862 -5.23% [ -6.80%, -3.63%] 4K 2.034 1.887 -7.21% [ -8.67%, -5.72%] 8K 1.664 1.568 -5.78% [ -7.83%, -3.69%] 16K 1.450 1.385 -4.48% [ -6.08%, -2.86%] 64K 1.338 1.317 -1.51% [ -3.21%, +0.22%] P1-P3 contribution: payload baseline RX PATCH RX throughput change (95% CI) (Gbit/s) (Gbit/s) 64B 0.1285 0.2462 +91.59% [+79.74%, +104.22%] 256B 0.5909 0.9666 +63.59% [+61.03%, +66.19%] 512B 1.1817 1.8350 +55.29% [+46.76%, +64.32%] 1K 2.3252 3.3600 +44.50% [+38.93%, +50.30%] 4K 3.8436 5.5661 +44.82% [+40.30%, +49.47%] 8K 4.6609 5.4115 +16.10% [ +8.91%, +23.77%] 16K 5.1196 5.6399 +10.16% [ +4.07%, +16.61%] 64K 5.6095 5.7062 +1.72% [-3.19%, +6.89%] Fixed-syscall stress test (receiver recv() size = sender write size; no perf; Gbit/s): payload baseline PATCH throughput change (95% CI) recv() RX RX (base/patch) (Gbit/s) (Gbit/s) 64B 0.1446 0.2540 +75.71% [+63.67%, +88.62%] 1048577/1048577 256B 0.4211 0.9061 +115.18% [+72.13%, +169.00%] 1048577/1048577 512B 0.7980 1.6112 +101.90% [+95.30%, +108.72%] 1048577/1048577 1K 1.4965 2.6986 +80.33% [+68.93%, +92.49%] 1048577/1048577 4K 2.9384 4.8590 +65.36% [+60.17%, +70.72%] 539544/524982 8K 3.8170 5.1887 +35.94% [+27.66%, +44.75%] 274857/262991 16K 4.6856 5.5996 +19.51% [+15.36%, +23.81%] 147518/131351 64K 5.5182 5.8800 +6.56% [-0.83%, +14.49%] 48492/32910 Guest CPU1 aggregate cycles per received byte (fixed 64K receiver, with perf): Buffer size baseline cycles/B PATCH cycles/B cycles change (95% CI) 64B 66.728 61.220 -8.25% [-18.99%, +3.91%] 256B 14.363 14.515 +1.06% [ -4.22%, +6.64%] 512B 7.792 7.578 -2.74% [ -6.55%, +1.23%] 1K 3.988 4.032 +1.09% [ -1.64%, +3.88%] 4K 2.063 1.973 -4.38% [ -8.23%, -0.37%] 8K 1.702 1.667 -2.06% [ -7.99%, +4.25%] 16K 1.473 1.475 +0.17% [ -5.06%, +5.68%] 64K 1.385 1.358 -1.96% [-10.61%, +7.53%] P4-P5 contribution (combined): End-to-end RX throughput (64K Guest recv() size, SO_RCVLOWAT=1; Gbit/s): payload P1-P3 RX P1-P5 RX throughput change (95% CI) (Gbit/s) (Gbit/s) 64B 0.2449 0.2463 +0.55% [-3.86%, +5.17%] 256B 0.9649 0.9931 +2.93% [+0.83%, +5.07%] 512B 1.8205 1.8260 +0.30% [-4.27%, +5.10%] 1K 3.3431 3.3420 -0.03% [-2.15%, +2.12%] 4K 5.6541 5.8428 +3.34% [+1.10%, +5.63%] 8K 5.4280 5.3364 -1.69% [-15.55%, +14.46%] 16K 5.5935 5.6701 +1.37% [-1.41%, +4.23%] 64K 5.6917 5.8351 +2.52% [-0.20%, +5.31%] Fixed-syscall stress test (receiver recv() size = sender write size; Gbit/s): payload P1-P3 P1-P5 throughput change (95% CI) recv() RX RX (P1-P3/P1-P5) (Gbit/s) (Gbit/s) 64B 0.2553 0.2575 +0.87% [-3.68%, +5.63%] 1048577/1048577 256B 0.9069 0.9183 +1.26% [-3.96%, +6.76%] 1048577/1048577 512B 1.6048 1.6459 +2.56% [+0.98%, +4.18%] 1048577/1048577 1K 2.6939 2.7357 +1.55% [-1.35%, +4.54%] 1048577/1048577 4K 4.9168 4.9678 +1.04% [-1.84%, +4.00%] 524965/525283 8K 5.1476 5.2005 +1.03% [-4.02%, +6.34%] 262926/263156 16K 5.5964 5.6609 +1.15% [-2.86%, +5.33%] 131311/131475 64K 5.9439 5.9073 -0.62% [-3.00%, +1.83%] 32875/32937 Guest CPU1 aggregate cycles per received byte (fixed 64K receiver, with perf): payload P1-P3 P1-P5 change (95% CI) 64B 60.281 58.258 -3.36% [-8.74%, +2.35%] 256B 14.242 13.648 -4.17% [-9.81%, +1.82%] 512B 7.547 7.211 -4.45% [-9.73%, +1.13%] 1K 3.987 3.853 -3.35% [-8.52%, +2.12%] 4K 1.983 1.880 -5.17% [-7.97%, -2.27%] 8K 1.665 1.620 -2.75% [-9.03%, +3.96%] 16K 1.409 1.346 -4.52% [-10.94%, +2.37%] 64K 1.322 1.281 -3.11% [-6.49%, +0.38%] --- This rerun used a stable host with a single Guest running and no background workload. The baseline throughput is higher and more stable than in v4, and the previous anomalous 4K throughput spike was not reproduced, confirming it was an artifact of host-side scheduling jitter. Consequently, while the absolute throughput numbers differ due to the cleaner host environment, the relative CPU cycle savings and syscall reductions remain consistent and robust. v5: - split the former batching patch into a metadata-budget helper (patch 2) and the batching policy itself (patch 3) - retain write-space coalescing and deferred data-ready handling as separate patches (patches 4 and 5) - document why a connected lookup type mismatch returns to the regular receive path, which sends the reset - restore reverse-Christmas-tree declaration order in the batch helpers - add the requested cap rationale, guest-virtio-only scope explanation, and cumulative performance results to patch 3 - add cumulative full-series performance results to patch 5 and identify the P4/P5 result as a combined measurement - use AF_VSOCK helpers for native callback access and save native callbacks before socket publication - serialize callback/protocol/psock eligibility checks with sk_callback_lock at every notification batch boundary - make the callback timing dependency explicit: patch 4 retains the under-lock context and patch 5 moves both notification types after release_sock() - share the receive low-watermark predicate between the ordinary and deferred data-ready paths - clarify the caller-provided network namespace and locking contract in the preparatory lookup split v4: - use only the connected socket lookup for batch admission and return misses to the normal receive path - read packet-specific addresses from the skb in the locked receive helper and use the matched socket namespace for reset replies - remove the extra address and network namespace arguments from the locked receive helper v3: - restrict RX batching to sockets using the original protocol and data-ready/write-space callbacks - exclude sockets carrying the psock marker published before sockmap protocol/callback replacement, and recheck it at each packet boundary - preserve existing sockmap update return values; an attach racing a native batch makes the next packet end the batch without queued-skb handoff - remove a leftover blank line after an opening brace - remove callback handoff work and attach/detach kicks, preserving the existing per-packet behavior for sockmap and other non-native sockets - avoid making this series drain queued or partially consumed skbs when a socket is added to or removed from a sockmap - clarify that Patch 1 prepares for batching and intends no functional change - inline address decoding and receive tracing, simplify the socket lookup helper, and pass locked receive arguments directly - fold same-flow lookup reuse into Patch 2 and match packets against the locked socket state, reducing the series from five patches to four v2: - stop a batch after it consumes the last skb metadata slot, sharing the admission predicate with virtio_transport_inc_rx_pkt() - move replacement-callback handoff into vsock, process queued skbs one at a time, and trigger the handoff from vsock_bpf_update_proto() on attach and detach - reduce the packet-context diff in the locked receive helper - keep RX batch counters in the batch state and reset them in the finish path - use the vsock/virtio subject prefix and add the requested measurements v1: https://lore.kernel.org/virtualization/20261002074551.318789-1-physicalmtea@gmail.com/ Jia Jia (5): vsock/virtio: split socket lookup from locked RX processing vsock/virtio: factor RX skb metadata budget check vsock/virtio: amortize RX socket locking for stream packets vsock/virtio: coalesce native RX write-space notifications vsock/virtio: defer native RX readiness notifications until batch unlock include/linux/virtio_vsock.h | 26 ++ include/net/af_vsock.h | 11 + net/vmw_vsock/af_vsock.c | 45 ++- net/vmw_vsock/virtio_transport.c | 7 +- net/vmw_vsock/virtio_transport_common.c | 440 +++++++++++++++++++++--- 5 files changed, 471 insertions(+), 58 deletions(-) base-commit: 8df0638138d3e0344fd1fb36cf2d1ca1cf5028f0 -- 2.34.1