Shailabh Nagar wrote:
> It would be interesting to see the performance boost when <iov length>
> are retrieved at once, using the min_nr parameter of io_getevents
My experience is that specified minimum number of events (min_nr) of
io_getevents is not quite working yet in kernel 2.4.19.
I haven't started to exercise this in 2.5.42, but if it is working,
logically it will help the performance indeed.
Shailabh Nagar <firstname.lastname@example.org>@kvack.org on 10/16/2002 08:41:03 AM
Sent by: email@example.com
cc: Benjamin LaHaise <firstname.lastname@example.org>, Christoph Hellwig <email@example.com>,
Subject: Re: [RFC] iovec in ->aio_read/->aio_write
Janet Morgan wrote:
> Here's a patch for aio readv/writev support. Basically it adds:
> - two new opcodes (IOCB_CMD_PREADV and IOCB_CMD_PWRITEV)
> - a field to the iocb for the user vector
> - aio_readv/writev methods to the file_operations structure
I presume f_op->aio_readv could point to __generic_file_aio_read for most
Would f_op->aio_writev need a new wrapper function for 2.5.42 ?
f_op->aio_write eventually calls generic_file_write which uses a different
from generic_file_writev. So f_op->aio_writev might need to point to a
like generic_file_writev but using the same inode as generic_file_write.
> - routine aio.c/io_readv_writev, which borrows heavily from
> I tested this using the aio dio patch that Badari submitted a while back.
> I compared:
> readv/writev io_submit for a vector of N iovecs
> vs read/write io_submit for N iocbs.
> My performance data is only preliminary at this point, but aio
> appears to outperform aio read/write -- twice as fast in some cases. The
> results generally make sense to me: while there is only one io_submit in
> cases, aio readv/writev shortens codepath (one instead of N calls to the
> underlying filesystem routine) and should normally result in fewer
Twice as fast looks good !
> bios/callbacks (at least for direct-io). As importantly, aio
> in my testing also reduces the number of (system) calls to io_getevents.
It would be interesting to see the performance boost when <iov length>
are retrieved at once, using the min_nr parameter of io_getevents.
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