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Tue, 20 Feb 2024 22:10:45 -0800 (PST) MIME-Version: 1.0 References: <20240220064414.262582-1-21cnbao@gmail.com> <20240220064414.262582-4-21cnbao@gmail.com> In-Reply-To: From: Barry Song <21cnbao@gmail.com> Date: Wed, 21 Feb 2024 19:10:33 +1300 Message-ID: Subject: Re: [PATCH v5 3/3] crypto: scompress: remove memcpy if sg_nents is 1 To: Herbert Xu , akpm@linux-foundation.org Cc: davem@davemloft.net, hannes@cmpxchg.org, linux-crypto@vger.kernel.org, linux-mm@kvack.org, nphamcs@gmail.com, yosryahmed@google.com, zhouchengming@bytedance.com, chriscli@google.com, chrisl@kernel.org, ddstreet@ieee.org, linux-kernel@vger.kernel.org, sjenning@redhat.com, vitaly.wool@konsulko.com, Barry Song Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 697C840003 X-Stat-Signature: a5rbadauio3gern7iy1ttxgrejbhrogj X-HE-Tag: 1708495846-294529 X-HE-Meta: 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 81Rz8f42 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Feb 21, 2024 at 6:55=E2=80=AFPM Barry Song <21cnbao@gmail.com> wrot= e: > > On Wed, Feb 21, 2024 at 6:35=E2=80=AFPM Herbert Xu wrote: > > > > On Tue, Feb 20, 2024 at 07:44:14PM +1300, Barry Song wrote: > > > From: Barry Song > > > > > > while sg_nents is 1 which is always true for the current kernel > > > as the only user - zswap is the case, we should remove two big > > > memcpy. > > > > > > Signed-off-by: Barry Song > > > Tested-by: Chengming Zhou > > > --- > > > crypto/scompress.c | 36 +++++++++++++++++++++++++++++------- > > > 1 file changed, 29 insertions(+), 7 deletions(-) > > > > This patch is independent of the other two. Please split it > > out so I can apply it directly. > > Ok. OTOH, patch 3/3 has no dependency with other patches. so patch > 3/3 should be perfectly applicable to crypto :-) > > Hi Andrew, > Would you please handle patch 1/3 and 2/3 in mm-tree given Herbert's ack = on > 1/3? > > > > > > @@ -134,13 +135,25 @@ static int scomp_acomp_comp_decomp(struct acomp= _req *req, int dir) > > > scratch =3D raw_cpu_ptr(&scomp_scratch); > > > spin_lock(&scratch->lock); > > > > > > - scatterwalk_map_and_copy(scratch->src, req->src, 0, req->slen, = 0); > > > + if (sg_nents(req->src) =3D=3D 1) { > > > + src =3D kmap_local_page(sg_page(req->src)) + req->src->= offset; > > > > What if the SG entry is longer than PAGE_SIZE (or indeed crosses a > > page boundary)? I think the test needs to be strengthened. > > I don't understand what is the problem for a nents to cross two pages > as anyway they are contiguous in both physical and virtual addresses. > if they are not contiguous, they will be two nents. second thought, you are right. sorry for my noise. The test was running on a platform like arm64 without HIGHMEM. thus, kmap_local_page always returns mapped page_address of normal zone. but for platforms with HIGHMEM for example arm32, x86_32 , we can't use the virtual address of the first page as the start address of two pages tho= ugh they are physically contiguous. I will rework on this. ideally, we should still avoid the memcpy though two pages are within one nents :-) we are really this case for zswap as the dst is always two pages in case the compressed data is longer than the original data. > > > > > Thanks, > > -- > > Email: Herbert Xu > > Home Page: http://gondor.apana.org.au/~herbert/ > > PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt > Thanks Barry