From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757178AbaGWN0K (ORCPT ); Wed, 23 Jul 2014 09:26:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:29417 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752798AbaGWN0I (ORCPT ); Wed, 23 Jul 2014 09:26:08 -0400 From: Jeff Moyer To: Gu Zheng Cc: bcrl@kvack.org, axboe@kernel.dk, akpm@linux-foundation.org, linux-aio@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RESEND PATCH 4/4] aio: use iovec array rather than the single one References: <1406109834-4414-1-git-send-email-guz.fnst@cn.fujitsu.com> <1406109834-4414-4-git-send-email-guz.fnst@cn.fujitsu.com> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Wed, 23 Jul 2014 09:25:57 -0400 In-Reply-To: <1406109834-4414-4-git-send-email-guz.fnst@cn.fujitsu.com> (Gu Zheng's message of "Wed, 23 Jul 2014 18:03:54 +0800") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Gu Zheng writes: > Previously, we only offer a single iovec to handle all the read/write cases, so > the PREADV/PWRITEV request always need to alloc more iovec buffer when copying > user vectors. > If we use a tmp iovec array rather than the single one, some small PREADV/PWRITEV > workloads(vector size small than the tmp buffer) will not need to alloc more > iovec buffer when copying user vectors. Hi, Gu, This still doesn't explain why you decided to look into this. Did you notice a performance issue in this path? Do you have benchmarks that show some speedup due to this change? Thanks, Jeff > > Reviewed-by: Jeff Moyer > Signed-off-by: Gu Zheng > --- > fs/aio.c | 10 +++++----- > 1 files changed, 5 insertions(+), 5 deletions(-) > > diff --git a/fs/aio.c b/fs/aio.c > index f1fede2..df3491a 100644 > --- a/fs/aio.c > +++ b/fs/aio.c > @@ -1267,12 +1267,12 @@ static ssize_t aio_setup_vectored_rw(struct kiocb *kiocb, > if (compat) > ret = compat_rw_copy_check_uvector(rw, > (struct compat_iovec __user *)buf, > - *nr_segs, 1, *iovec, iovec); > + *nr_segs, UIO_FASTIOV, *iovec, iovec); > else > #endif > ret = rw_copy_check_uvector(rw, > (struct iovec __user *)buf, > - *nr_segs, 1, *iovec, iovec); > + *nr_segs, UIO_FASTIOV, *iovec, iovec); > if (ret < 0) > return ret; > > @@ -1309,7 +1309,7 @@ static ssize_t aio_run_iocb(struct kiocb *req, unsigned opcode, > fmode_t mode; > aio_rw_op *rw_op; > rw_iter_op *iter_op; > - struct iovec inline_vec, *iovec = &inline_vec; > + struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs; > struct iov_iter iter; > > switch (opcode) { > @@ -1344,7 +1344,7 @@ rw_common: > if (!ret) > ret = rw_verify_area(rw, file, &req->ki_pos, req->ki_nbytes); > if (ret < 0) { > - if (iovec != &inline_vec) > + if (iovec != inline_vecs) > kfree(iovec); > return ret; > } > @@ -1391,7 +1391,7 @@ rw_common: > return -EINVAL; > } > > - if (iovec != &inline_vec) > + if (iovec != inline_vecs) > kfree(iovec); > > if (ret != -EIOCBQUEUED) {