| Re: [PATCH v2 00/11] fuse: optimize scatter-gather direct IO [message #48415 is a reply to message #47948] |
Tue, 16 October 2012 17:32  |
Maxim Patlasov
Messages: 45
Registered: July 2012
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Member |
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Hi Miklos,
09/19/2012 08:31 PM, Maxim Patlasov пишет:
> 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
>
> ---
>
> 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(-)
>
Any feedback on this patch-set (v2) would be highly appreciated.
Thanks,
Maxim
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