From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:44190 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727737AbfGEOwg (ORCPT ); Fri, 5 Jul 2019 10:52:36 -0400 Date: Fri, 5 Jul 2019 10:52:33 -0400 From: Brian Foster Subject: Re: [PATCH 5/6] xfs: only allocate memory for scrubbing attributes when we need it Message-ID: <20190705145233.GG37448@bfoster> References: <156158199378.495944.4088787757066517679.stgit@magnolia> <156158202408.495944.3341471232105593997.stgit@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <156158202408.495944.3341471232105593997.stgit@magnolia> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org On Wed, Jun 26, 2019 at 01:47:04PM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong > > In examining a flame graph of time spent running xfs_scrub on various > filesystems, I noticed that we spent nearly 7% of the total runtime on > allocating a zeroed 65k buffer for every SCRUB_TYPE_XATTR invocation. > We do this even if none of the attribute values were anywhere near 64k > in size, even if there were no attribute blocks to check space on, and > even if it just turns out there are no attributes at all. > > Therefore, rearrange the xattr buffer setup code to support reallocating > with a bigger buffer and redistribute the callers of that function so > that we only allocate memory just prior to needing it, and only allocate > as much as we need. If we can't get memory with the ILOCK held we'll > bail out with EDEADLOCK which will allocate the maximum memory. > > Signed-off-by: Darrick J. Wong > --- > fs/xfs/scrub/attr.c | 67 ++++++++++++++++++++++++++++++++++++++++++++------- > fs/xfs/scrub/attr.h | 6 ++++- > 2 files changed, 63 insertions(+), 10 deletions(-) > > > diff --git a/fs/xfs/scrub/attr.c b/fs/xfs/scrub/attr.c > index c20b6da1db84..09081d8ab34b 100644 > --- a/fs/xfs/scrub/attr.c > +++ b/fs/xfs/scrub/attr.c ... > @@ -47,10 +53,23 @@ xchk_setup_xattr_buf( > sz = 3 * sizeof(long) * BITS_TO_LONGS(sc->mp->m_attr_geo->blksize); > sz = max_t(size_t, sz, value_size); > > - sc->buf = kmem_zalloc_large(sz, KM_SLEEP); > - if (!sc->buf) > + /* > + * If there's already a buffer, figure out if we need to reallocate it > + * to accomdate a larger size. accommodate Otherwise looks good: Reviewed-by: Brian Foster > + */ > + if (ab) { > + if (sz <= ab->sz) > + return 0; > + kmem_free(ab); > + sc->buf = NULL; > + } > + > + ab = kmem_zalloc_large(sizeof(*ab) + sz, flags); > + if (!ab) > return -ENOMEM; > > + ab->sz = sz; > + sc->buf = ab; > return 0; > } > > @@ -62,9 +81,16 @@ xchk_setup_xattr( > { > int error; > > - error = xchk_setup_xattr_buf(sc, XATTR_SIZE_MAX); > - if (error) > - return error; > + /* > + * We failed to get memory while checking attrs, so this time try to > + * get all the memory we're ever going to need. Allocate the buffer > + * without the inode lock held, which means we can sleep. > + */ > + if (sc->flags & XCHK_TRY_HARDER) { > + error = xchk_setup_xattr_buf(sc, XATTR_SIZE_MAX, KM_SLEEP); > + if (error) > + return error; > + } > > return xchk_setup_inode_contents(sc, ip, 0); > } > @@ -115,6 +141,19 @@ xchk_xattr_listent( > return; > } > > + /* > + * Try to allocate enough memory to extrat the attr value. If that > + * doesn't work, we overload the seen_enough variable to convey > + * the error message back to the main scrub function. > + */ > + error = xchk_setup_xattr_buf(sx->sc, valuelen, KM_MAYFAIL); > + if (error == -ENOMEM) > + error = -EDEADLOCK; > + if (error) { > + context->seen_enough = error; > + return; > + } > + > args.flags = ATTR_KERNOTIME; > if (flags & XFS_ATTR_ROOT) > args.flags |= ATTR_ROOT; > @@ -128,7 +167,7 @@ xchk_xattr_listent( > args.hashval = xfs_da_hashname(args.name, args.namelen); > args.trans = context->tp; > args.value = xchk_xattr_valuebuf(sx->sc); > - args.valuelen = XATTR_SIZE_MAX; > + args.valuelen = valuelen; > > error = xfs_attr_get_ilocked(context->dp, &args); > if (error == -EEXIST) > @@ -281,16 +320,26 @@ xchk_xattr_block( > struct xfs_attr_leafblock *leaf = bp->b_addr; > struct xfs_attr_leaf_entry *ent; > struct xfs_attr_leaf_entry *entries; > - unsigned long *usedmap = xchk_xattr_usedmap(ds->sc); > + unsigned long *usedmap; > char *buf_end; > size_t off; > __u32 last_hashval = 0; > unsigned int usedbytes = 0; > unsigned int hdrsize; > int i; > + int error; > > if (*last_checked == blk->blkno) > return 0; > + > + /* Allocate memory for block usage checking. */ > + error = xchk_setup_xattr_buf(ds->sc, 0, KM_MAYFAIL); > + if (error == -ENOMEM) > + return -EDEADLOCK; > + if (error) > + return error; > + usedmap = xchk_xattr_usedmap(ds->sc); > + > *last_checked = blk->blkno; > bitmap_zero(usedmap, mp->m_attr_geo->blksize); > > diff --git a/fs/xfs/scrub/attr.h b/fs/xfs/scrub/attr.h > index 27e879aeaafc..13a1d2e8424d 100644 > --- a/fs/xfs/scrub/attr.h > +++ b/fs/xfs/scrub/attr.h > @@ -10,6 +10,9 @@ > * Temporary storage for online scrub and repair of extended attributes. > */ > struct xchk_xattr_buf { > + /* Size of @buf, in bytes. */ > + size_t sz; > + > /* > * Memory buffer -- either used for extracting attr values while > * walking the attributes; or for computing attr block bitmaps when > @@ -62,6 +65,7 @@ xchk_xattr_dstmap( > BITS_TO_LONGS(sc->mp->m_attr_geo->blksize); > } > > -int xchk_setup_xattr_buf(struct xfs_scrub *sc, size_t value_size); > +int xchk_setup_xattr_buf(struct xfs_scrub *sc, size_t value_size, > + xfs_km_flags_t flags); > > #endif /* __XFS_SCRUB_ATTR_H__ */ >