From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 31C472E7BB6; Mon, 30 Mar 2026 14:35:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774881350; cv=none; b=uqZzS9rgsgQjBbkJ9Di72S6phGC3+QwAd9e41FD4msSXIXFRhoF+1rxu19aGZ8/b3D+KaKVyO4E0P0DvyKr7DS01W27G9XlpJWGNH8GPskfRkAbQbs3Hi0DrdBGLkU2HznmcTDtTiwWbq2TbU+GzTF4iNFazyOqMbtqXmeUlhLM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774881350; c=relaxed/simple; bh=HHfxw1FEuQsMoLKCj7A+GvFmIFDI80BjaPMvstStO5I=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=V955bUOQf+4l34Cd8OjT/grBwZZ02xndSjoz0/Rxm5qmXG8YdByot3pnXFsx8l+7SIl7+QjFlpjP8iyEu4XSmv9w+hICYAOMjBZAoq0IMsfI/wXSiaucsaW8pnSnSjNXqd5HNbQfGozScyH+mvYNW9LkjQrwzSqfqmVU+ZSfsMo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UwtrSMPL; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UwtrSMPL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 11C51C4CEF7; Mon, 30 Mar 2026 14:35:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774881349; bh=HHfxw1FEuQsMoLKCj7A+GvFmIFDI80BjaPMvstStO5I=; h=Date:Subject:To:References:From:In-Reply-To:From; b=UwtrSMPLZX3sohAGKTRw7Rso3hDmHASdR/K06e9EScHVjSlNJbQRK3zAxVH5T6fbc u4y0GylbOG7ifiUhJ5gp1pSTCaMIaObdgpx6uPaYWs94+YBnmSCQGKi0FZe+ktCDnz yzD4QPupNGMywdcJZs+SXCS37xW0OhNXwu1Oz6FhJGwo49hqY4L8MDgSy2V3DXZ7+V yFkRjEucGrmteUIMKO70hW3kCrAFhSs0mHSUKt7DmhMtrAJctkXDwnKLE4cMDTXR4m Iy+J2xvnVjLYWe53LyWI+YiwY2sYNiZb/s7Hfl4mi8tphOzmijb9M01CtzHJ6Qflwx 9IHlTpT8wjjEg== Message-ID: <0039fdb2-b23d-4ada-8d83-595e7816521a@kernel.org> Date: Mon, 30 Mar 2026 16:35:44 +0200 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/3] vmalloc: Optimize vfree Content-Language: en-US To: Muhammad Usama Anjum , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Uladzislau Rezki , Nick Terrell , David Sterba , Vishal Moola , linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Ryan.Roberts@arm.com, david.hildenbrand@arm.com References: <20260327125720.2270651-1-usama.anjum@arm.com> <20260327125720.2270651-3-usama.anjum@arm.com> From: "Vlastimil Babka (SUSE)" In-Reply-To: <20260327125720.2270651-3-usama.anjum@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/27/26 13:57, Muhammad Usama Anjum wrote: > From: Ryan Roberts > > Whenever vmalloc allocates high order pages (e.g. for a huge mapping) it > must immediately split_page() to order-0 so that it remains compatible > with users that want to access the underlying struct page. > Commit a06157804399 ("mm/vmalloc: request large order pages from buddy > allocator") recently made it much more likely for vmalloc to allocate > high order pages which are subsequently split to order-0. > > Unfortunately this had the side effect of causing performance > regressions for tight vmalloc/vfree loops (e.g. test_vmalloc.ko > benchmarks). See Closes: tag. This happens because the high order pages > must be gotten from the buddy but then because they are split to > order-0, when they are freed they are freed to the order-0 pcp. > Previously allocation was for order-0 pages so they were recycled from > the pcp. > > It would be preferable if when vmalloc allocates an (e.g.) order-3 page > that it also frees that order-3 page to the order-3 pcp, then the > regression could be removed. > > So let's do exactly that; update stats separately first as coalescing is > hard to do correctly without complexity. Use free_pages_bulk() which uses > the new __free_contig_range() API to batch-free contiguous ranges of pfns. > This not only removes the regression, but significantly improves > performance of vfree beyond the baseline. > > A selection of test_vmalloc benchmarks running on arm64 server class > system. mm-new is the baseline. Commit a06157804399 ("mm/vmalloc: request > large order pages from buddy allocator") was added in v6.19-rc1 where we > see regressions. Then with this change performance is much better. (>0 > is faster, <0 is slower, (R)/(I) = statistically significant > Regression/Improvement): > > +-----------------+----------------------------------------------------------+-------------------+--------------------+ > | Benchmark | Result Class | mm-new | this series | > +=================+==========================================================+===================+====================+ > | micromm/vmalloc | fix_align_alloc_test: p:1, h:0, l:500000 (usec) | 1331843.33 | (I) 67.17% | > | | fix_size_alloc_test: p:1, h:0, l:500000 (usec) | 415907.33 | -5.14% | > | | fix_size_alloc_test: p:4, h:0, l:500000 (usec) | 755448.00 | (I) 53.55% | > | | fix_size_alloc_test: p:16, h:0, l:500000 (usec) | 1591331.33 | (I) 57.26% | > | | fix_size_alloc_test: p:16, h:1, l:500000 (usec) | 1594345.67 | (I) 68.46% | > | | fix_size_alloc_test: p:64, h:0, l:100000 (usec) | 1071826.00 | (I) 79.27% | > | | fix_size_alloc_test: p:64, h:1, l:100000 (usec) | 1018385.00 | (I) 84.17% | > | | fix_size_alloc_test: p:256, h:0, l:100000 (usec) | 3970899.67 | (I) 77.01% | > | | fix_size_alloc_test: p:256, h:1, l:100000 (usec) | 3821788.67 | (I) 89.44% | > | | fix_size_alloc_test: p:512, h:0, l:100000 (usec) | 7795968.00 | (I) 82.67% | > | | fix_size_alloc_test: p:512, h:1, l:100000 (usec) | 6530169.67 | (I) 118.09% | > | | full_fit_alloc_test: p:1, h:0, l:500000 (usec) | 626808.33 | -0.98% | > | | kvfree_rcu_1_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 532145.67 | -1.68% | > | | kvfree_rcu_2_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 537032.67 | -0.96% | > | | long_busy_list_alloc_test: p:1, h:0, l:500000 (usec) | 8805069.00 | (I) 74.58% | > | | pcpu_alloc_test: p:1, h:0, l:500000 (usec) | 500824.67 | 4.35% | > | | random_size_align_alloc_test: p:1, h:0, l:500000 (usec) | 1637554.67 | (I) 76.99% | > | | random_size_alloc_test: p:1, h:0, l:500000 (usec) | 4556288.67 | (I) 72.23% | > | | vm_map_ram_test: p:1, h:0, l:500000 (usec) | 107371.00 | -0.70% | > +-----------------+----------------------------------------------------------+-------------------+--------------------+ > > Fixes: a06157804399 ("mm/vmalloc: request large order pages from buddy allocator") > Closes: https://lore.kernel.org/all/66919a28-bc81-49c9-b68f-dd7c73395a0d@arm.com/ > Acked-by: Zi Yan > Signed-off-by: Ryan Roberts > Co-developed-by: Muhammad Usama Anjum > Signed-off-by: Muhammad Usama Anjum Acked-by: Vlastimil Babka (SUSE)