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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <3710261.1691764329@warthog.procyon.org.uk> To: Linus Torvalds Cc: dhowells@redhat.com, Alexander Viro , Jens Axboe , Christoph Hellwig , Christian Brauner , Matthew Wilcox , jlayton@kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] iov_iter: Convert iterate*() to inline funcs MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <3888330.1691773627.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Fri, 11 Aug 2023 18:07:07 +0100 Message-ID: <3888331.1691773627@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: D27CE40024 X-Stat-Signature: q7uxbontsw6418oe4xatdqbji4yddoh3 X-Rspam-User: X-HE-Tag: 1691773633-360548 X-HE-Meta: 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 hqHnowPc 3WsAe6MoYhEzzc1rXWJ68lFRSPqqisVwJejBiGUevsS8l7F2ebT5oZbMU3dF+xLWclCfdPJutvFdugpMAxJJR01Pi5LS/na4CEi6LT3FCnJCmWSC8xS2OUNhAAxDQFT53wmbSu4yRmDx6r6Fx4Bf/jJyorIw/zdHiDsynxDi/s2dxczFDgnoj+KSHSo8xhZ3Z5ckGJH6ChEwB8sKW+XEx2yr2k6rudkxah/bBVkEdY3iEZCfR70GRB81hZNZpO2A+A0EGQiQqIZeWzqY= 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: Linus Torvalds wrote: > I like this generally, the code generation deprovement worries me a > bit, but from a quick look on a test-branch it didn't really look all > that bad (but the changes are too big to usefully show up as asm > diffs) Hmmm... It seems that using if-if-if rather than switch() gets optimised better in terms of .text space. The attached change makes things a bit smaller (by 69 bytes). David --- diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 8943ac25e202..f61474ec1c89 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -190,22 +190,18 @@ size_t iterate_and_advance(struct iov_iter *iter, si= ze_t len, void *priv, if (unlikely(!len)) return 0; = - switch (iov_iter_type(iter)) { - case ITER_UBUF: + if (likely(iter_is_ubuf(iter))) return iterate_ubuf(iter, len, priv, NULL, ustep); - case ITER_IOVEC: + if (likely(iter_is_iovec(iter))) return iterate_iovec(iter, len, priv, NULL, ustep); - case ITER_KVEC: + if (iov_iter_is_kvec(iter)) return iterate_kvec(iter, len, priv, NULL, step); - case ITER_BVEC: + if (iov_iter_is_bvec(iter)) return iterate_bvec(iter, len, priv, NULL, step); - case ITER_XARRAY: + if (iov_iter_is_xarray(iter)) return iterate_xarray(iter, len, priv, NULL, step); - case ITER_DISCARD: - iter->count -=3D len; - return len; - } - return 0; + iter->count -=3D len; + return len; } = static __always_inline @@ -217,22 +213,18 @@ size_t iterate_and_advance_csum(struct iov_iter *ite= r, size_t len, void *priv, if (unlikely(!len)) return 0; = - switch (iov_iter_type(iter)) { - case ITER_UBUF: + if (likely(iter_is_ubuf(iter))) return iterate_ubuf(iter, len, priv, csum, ustep); - case ITER_IOVEC: + if (likely(iter_is_iovec(iter))) return iterate_iovec(iter, len, priv, csum, ustep); - case ITER_KVEC: + if (iov_iter_is_kvec(iter)) return iterate_kvec(iter, len, priv, csum, step); - case ITER_BVEC: + if (iov_iter_is_bvec(iter)) return iterate_bvec(iter, len, priv, csum, step); - case ITER_XARRAY: + if (iov_iter_is_xarray(iter)) return iterate_xarray(iter, len, priv, csum, step); - case ITER_DISCARD: - iter->count -=3D len; - return len; - } - return 0; + iter->count -=3D len; + return len; } = static size_t copy_to_user_iter(void __user *iter_to, size_t progress,