From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-118.freemail.mail.aliyun.com (out30-118.freemail.mail.aliyun.com [115.124.30.118]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CE77C8F6C for ; Thu, 17 Oct 2024 03:25:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.118 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729135547; cv=none; b=qP0L8evp1Si+iMH1bDtf38fWYycsVQDr4KlHSILNw1kWn0JSbjfCjdN0maCCK/T34+4wPXhFUo3nBS81Vr1w3y9OMhgGpj9pgGyiUAa0lOYziUfapu4ZFYXVn1Piv45GtEvFXSVEHjHBkai6dzZ8ywi4ApfbpQOV8M3I9Ts/i1U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729135547; c=relaxed/simple; bh=imCL1m4BIcB95ncEb8kEhZkGxOtX4M/m1Anw4W4/2N0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=bPte19GZjBnQzfda/w3u2zUxV7VpjZG7QeA6TGWQp1SOLYFXeEVzQeT4+H2BEdN1aulQY6m86GIglFxKYRwjgxV1zZ4MO+zx2wk93uIFe9h2B5bpTLwv+tlyXVDDEPqPOux6njT/WQMeh/x1RGbiX8S8XH4ra9o4sQGloADL3rU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=XVgh+yOu; arc=none smtp.client-ip=115.124.30.118 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="XVgh+yOu" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1729135541; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=9WfeWxzTjli81jKhloyV8TsWg0tcegzsoqDI3F/SNH8=; b=XVgh+yOuSzBofOrDfepGDsXn7wdhC2T4MOquoiwW6GFbx22m5nlxh7qiBqFsXQtlO5Gn3yFht1l/P0qzr9Q1t5IEX+SFS5HgTmDbWbB5mqKcggFYFHfCHc5vXp0EJJAjttlQSOhiXpptBlP6mvCPdBhsStngFA2bbHcrr7ZwxTk= Received: from 30.74.144.140(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WHJGsIc_1729135540 cluster:ay36) by smtp.aliyun-inc.com; Thu, 17 Oct 2024 11:25:40 +0800 Message-ID: <2b3572e1-a618-4f86-979d-87f59282fe8f@linux.alibaba.com> Date: Thu, 17 Oct 2024 11:25:39 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] mm: shmem: improve the tmpfs large folio read performance To: Yang Shi , Matthew Wilcox Cc: akpm@linux-foundation.org, hughd@google.com, david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2024/10/17 01:33, Yang Shi wrote: > On Wed, Oct 16, 2024 at 8:38 AM Matthew Wilcox wrote: >> >> On Wed, Oct 16, 2024 at 06:09:30PM +0800, Baolin Wang wrote: >>> @@ -3128,8 +3127,9 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) >>> if (folio) { >>> folio_unlock(folio); >>> >>> - page = folio_file_page(folio, index); >>> - if (PageHWPoison(page)) { >>> + if (folio_test_hwpoison(folio) || >>> + (folio_test_large(folio) && >>> + folio_test_has_hwpoisoned(folio))) { >> >> Hm, so if we have hwpoison set on one page in a folio, we now can't read >> bytes from any page in the folio? That seems like we've made a bad >> situation worse. > > Yeah, I agree. I think we can fallback to page copy if > folio_test_has_hwpoisoned is true. The PG_hwpoison flag is per page. > > The folio_test_has_hwpoisoned is kept set if the folio split is failed > in memory failure handler. Right. I can still keep the page size copy if folio_test_has_hwpoisoned() is true. Some sample changes are as follow. Moreover, I noticed shmem splice_read() and write() also simply return an error if the folio_test_has_hwpoisoned() is true, without any fallback to page granularity. I wonder if it is worth adding page granularity support as well? diff --git a/mm/shmem.c b/mm/shmem.c index 7e79b6a96da0..f30e24e529b9 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3111,9 +3111,11 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) for (;;) { struct folio *folio = NULL; + struct page *page = NULL; unsigned long nr, ret; loff_t end_offset, i_size = i_size_read(inode); size_t fsize; + bool fallback_page_copy = false; if (unlikely(iocb->ki_pos >= i_size)) break; @@ -3127,13 +3129,16 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) if (folio) { folio_unlock(folio); - if (folio_test_hwpoison(folio) || - (folio_test_large(folio) && - folio_test_has_hwpoisoned(folio))) { + page = folio_file_page(folio, index); + if (PageHWPoison(page)) { folio_put(folio); error = -EIO; break; } + + if (folio_test_large(folio) && + folio_test_has_hwpoisoned(folio)) + fallback_page_copy = true; } /* @@ -3147,7 +3152,7 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) break; } end_offset = min_t(loff_t, i_size, iocb->ki_pos + to->count); - if (folio) + if (folio && likely(!fallback_page_copy)) fsize = folio_size(folio); else fsize = PAGE_SIZE; @@ -3160,8 +3165,13 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) * virtual addresses, take care about potential aliasing * before reading the page on the kernel side. */ - if (mapping_writably_mapped(mapping)) - flush_dcache_folio(folio); + if (mapping_writably_mapped(mapping)) { + if (unlikely(fallback_page_copy)) + flush_dcache_page(page); + else + flush_dcache_folio(folio); + } + /* * Mark the page accessed if we read the beginning. */ @@ -3171,7 +3181,10 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) * Ok, we have the page, and it's up-to-date, so * now we can copy it to user space... */ - ret = copy_folio_to_iter(folio, offset, nr, to); + if (unlikely(fallback_page_copy)) + ret = copy_page_to_iter(page, offset, nr, to); + else + ret = copy_folio_to_iter(folio, offset, nr, to); folio_put(folio); } else if (user_backed_iter(to)) { /*