Messages in this thread | | | Subject | [PATCH v2 00/11] fuse: optimize scatter-gather direct IO | From | Maxim Patlasov <> | Date | Wed, 19 Sep 2012 20:31:10 +0400 |
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Hi,
Existing fuse implementation processes scatter-gather direct IO in suboptimal way: fuse_direct_IO passes iovec[] to fuse_loop_dio and the latter calls fuse_direct_read/write for each iovec from iovec[] array. Thus we have as many submitted fuse-requests as the number of elements in iovec[] array. This is pure waste of resources and affects performance negatively especially for the case of many small chunks (e.g. page-size) packed in one iovec[] array.
The patch-set amends situation in a natural way: let's simply pack as many iovec[] segments to every fuse-request as possible.
To estimate performance improvement I used slightly modified fusexmp over tmpfs (clearing O_DIRECT bit from fi->flags in xmp_open). The test opened a file with O_DIRECT, then called readv/writev in a loop. An iovec[] for readv/writev consisted of 32 segments of 4K each. The throughput on some commodity (rather feeble) server was (in MB/sec):
original / patched writev: ~107 / ~480 readv: ~114 / ~569
We're exploring possibility to use fuse for our own distributed storage implementation and big iovec[] arrays of many page-size chunks is typical use-case for device virtualization thread performing i/o on behalf of virtual-machine it serves.
Changed in v2: - inline array of page pointers req->pages[] is replaced with dynamically allocated one; the number of elements is calculated a bit more intelligently than being equal to FUSE_MAX_PAGES_PER_REQ; this is done for the sake of memory economy. - a dynamically allocated array of so-called 'page descriptors' - an offset in page plus the length of fragment - is added to fuse_req; this is done to simplify processing fuse requests covering several iov-s.
Thanks, Maxim
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Maxim Patlasov (11): fuse: general infrastructure for pages[] of variable size fuse: categorize fuse_get_req() fuse: rework fuse_retrieve() fuse: rework fuse_readpages() fuse: rework fuse_perform_write() fuse: rework fuse_do_ioctl() fuse: add per-page descriptor <offset, length> to fuse_req fuse: use req->page_descs[] for argpages cases fuse: pass iov[] to fuse_get_user_pages() fuse: optimize fuse_get_user_pages() fuse: optimize __fuse_direct_io()
fs/fuse/cuse.c | 3 - fs/fuse/dev.c | 96 ++++++++++++++------- fs/fuse/dir.c | 39 ++++---- fs/fuse/file.c | 250 ++++++++++++++++++++++++++++++++++++------------------ fs/fuse/fuse_i.h | 47 ++++++++-- fs/fuse/inode.c | 6 + 6 files changed, 296 insertions(+), 145 deletions(-)
-- Signature
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