Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751709Ab3JRIK2 (ORCPT ); Fri, 18 Oct 2013 04:10:28 -0400 Received: from cantor2.suse.de ([195.135.220.15]:37915 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751217Ab3JRIKS (ORCPT ); Fri, 18 Oct 2013 04:10:18 -0400 Message-ID: <5260ECE2.6010106@suse.cz> Date: Fri, 18 Oct 2013 10:10:10 +0200 From: Vlastimil Babka User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.0 MIME-Version: 1.0 To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Alexander Viro , Rik van Riel , Andrea Arcangeli , Dave Hansen , Matt Helsley , Anthony Liguori , Michael Roth , Lei Li , Leonardo Garcia Subject: Re: [PATCH 1/2] vmsplice: unmap gifted pages for recipient References: <1381177293-27125-1-git-send-email-rcj@linux.vnet.ibm.com> <1381177293-27125-2-git-send-email-rcj@linux.vnet.ibm.com> <525FB9EE.3070609@suse.cz> <20131017134827.GB19741@linux.vnet.ibm.com> In-Reply-To: <20131017134827.GB19741@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5803 Lines: 173 On 10/17/2013 03:48 PM, Robert Jennings wrote: > * Vlastimil Babka (vbabka@suse.cz) wrote: >> On 10/07/2013 10:21 PM, Robert C Jennings wrote: >>> Introduce use of the unused SPLICE_F_MOVE flag for vmsplice to zap >>> pages. >>> >>> When vmsplice is called with flags (SPLICE_F_GIFT | SPLICE_F_MOVE) the >>> writer's gift'ed pages would be zapped. This patch supports further work >>> to move vmsplice'd pages rather than copying them. That patch has the >>> restriction that the page must not be mapped by the source for the move, >>> otherwise it will fall back to copying the page. >>> >>> Signed-off-by: Matt Helsley >>> Signed-off-by: Robert C Jennings >>> --- >>> Since the RFC went out I have coalesced the zap_page_range() call to >>> operate on VMAs rather than calling this for each page. For a 256MB >>> vmsplice this reduced the write side 50% from the RFC. >>> --- >>> fs/splice.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++- >>> include/linux/splice.h | 1 + >>> 2 files changed, 51 insertions(+), 1 deletion(-) >>> >>> diff --git a/fs/splice.c b/fs/splice.c >>> index 3b7ee65..a62d61e 100644 >>> --- a/fs/splice.c >>> +++ b/fs/splice.c >>> @@ -188,12 +188,17 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe, >>> { >>> unsigned int spd_pages = spd->nr_pages; >>> int ret, do_wakeup, page_nr; >>> + struct vm_area_struct *vma; >>> + unsigned long user_start, user_end; >>> >>> ret = 0; >>> do_wakeup = 0; >>> page_nr = 0; >>> + vma = NULL; >>> + user_start = user_end = 0; >>> >>> pipe_lock(pipe); >>> + down_read(¤t->mm->mmap_sem); >> >> Seems like you could take the mmap_sem only when GIFT and MOVE is set. >> Maybe it won't help that much for performance but at least serve as >> documenting the reason it's needed? >> >> Vlastimil >> > > I had been doing that previously but moving this outside the loop and > acquiring it once did improve performance. I'll add a comment on > down_read() as to the reason for taking this though. > > -Rob Hm perhaps in light of recent patches to reduce mmap_sem usage only to really critical regions, maybe it really shouldn't be taken at all if not needed. Vlastimil >>> for (;;) { >>> if (!pipe->readers) { >>> @@ -212,8 +217,44 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe, >>> buf->len = spd->partial[page_nr].len; >>> buf->private = spd->partial[page_nr].private; >>> buf->ops = spd->ops; >>> - if (spd->flags & SPLICE_F_GIFT) >>> + if (spd->flags & SPLICE_F_GIFT) { >>> + unsigned long useraddr = >>> + spd->partial[page_nr].useraddr; >>> + >>> + if ((spd->flags & SPLICE_F_MOVE) && >>> + !buf->offset && >>> + (buf->len == PAGE_SIZE)) { >>> + /* Can move page aligned buf, gather >>> + * requests to make a single >>> + * zap_page_range() call per VMA >>> + */ >>> + if (vma && (useraddr == user_end) && >>> + ((useraddr + PAGE_SIZE) <= >>> + vma->vm_end)) { >>> + /* same vma, no holes */ >>> + user_end += PAGE_SIZE; >>> + } else { >>> + if (vma) >>> + zap_page_range(vma, >>> + user_start, >>> + (user_end - >>> + user_start), >>> + NULL); >>> + vma = find_vma_intersection( >>> + current->mm, >>> + useraddr, >>> + (useraddr + >>> + PAGE_SIZE)); >>> + if (!IS_ERR_OR_NULL(vma)) { >>> + user_start = useraddr; >>> + user_end = (useraddr + >>> + PAGE_SIZE); >>> + } else >>> + vma = NULL; >>> + } >>> + } >>> buf->flags |= PIPE_BUF_FLAG_GIFT; >>> + } >>> >>> pipe->nrbufs++; >>> page_nr++; >>> @@ -255,6 +296,10 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe, >>> pipe->waiting_writers--; >>> } >>> >>> + if (vma) >>> + zap_page_range(vma, user_start, (user_end - user_start), NULL); >>> + >>> + up_read(¤t->mm->mmap_sem); >>> pipe_unlock(pipe); >>> >>> if (do_wakeup) >>> @@ -485,6 +530,7 @@ fill_it: >>> >>> spd.partial[page_nr].offset = loff; >>> spd.partial[page_nr].len = this_len; >>> + spd.partial[page_nr].useraddr = index << PAGE_CACHE_SHIFT; >>> len -= this_len; >>> loff = 0; >>> spd.nr_pages++; >>> @@ -656,6 +702,7 @@ ssize_t default_file_splice_read(struct file *in, loff_t *ppos, >>> this_len = min_t(size_t, vec[i].iov_len, res); >>> spd.partial[i].offset = 0; >>> spd.partial[i].len = this_len; >>> + spd.partial[i].useraddr = (unsigned long)vec[i].iov_base; >>> if (!this_len) { >>> __free_page(spd.pages[i]); >>> spd.pages[i] = NULL; >>> @@ -1475,6 +1522,8 @@ static int get_iovec_page_array(const struct iovec __user *iov, >>> >>> partial[buffers].offset = off; >>> partial[buffers].len = plen; >>> + partial[buffers].useraddr = (unsigned long)base; >>> + base = (void*)((unsigned long)base + PAGE_SIZE); >>> >>> off = 0; >>> len -= plen; >>> diff --git a/include/linux/splice.h b/include/linux/splice.h >>> index 74575cb..56661e3 100644 >>> --- a/include/linux/splice.h >>> +++ b/include/linux/splice.h >>> @@ -44,6 +44,7 @@ struct partial_page { >>> unsigned int offset; >>> unsigned int len; >>> unsigned long private; >>> + unsigned long useraddr; >>> }; >>> >>> /* >>> >> > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/