Hi Tony,
The intention of the mmap-racache was to perform read ahead for files
that are mmapped. An example use case would be running an executable
off of PVFS. In that case, read ahead would be more efficient than
waiting for pages to be read in individually as needed.
In theory it shouldn't have any impact on iozone writes.
-Phil
Tony Kew wrote:
Dear Phil,
PVFS 2.8.1 works (insofar as I can tell) with the --enable-mmap-racache
configure option with the following patch:
--- src/apps/kernel/linux/pvfs2-client-core.c.orig 2009-02-27
15:53:50.000000000 -0500
+++ src/apps/kernel/linux/pvfs2-client-core.c 2009-02-27
15:54:22.000000000 -0500
@@ -1609,7 +1609,7 @@ static PVFS_error post_io_readahead_requ
&vfs_request->in_upcall.credentials,
&vfs_request->response.io,
vfs_request->in_upcall.req.io.io_type,
- &vfs_request->op_id, (void *)vfs_request);
+ &vfs_request->op_id, vfs_request->hints, (void *)vfs_request);
if (ret < 0)
{
I am, though, getting poor iozone performance numbers for initial write...
I'm going to run some more iozone tests & try without the
--enable-mmap-racache and let you know what I find...
Thanks,
Tony
Tony Kew
SAN Administrator
The Center for Computational Research
New York State Center of Excellence
in Bioinformatics & Life Sciences
701 Ellicott Street, Buffalo, NY 14203
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Tony Kew wrote:
Dear Phil,
Thanks for the info, the option worked for me with 7.2.1 codebase, for
what its worth. The 7.8.0 code with my patch works so far (with the very
limited tests I have done.) I'll be testing over several nodes this
afternoon,
or tomorrow.
[...]
Phil Carns wrote:
Hi Tony,
I just wanted to mention that the second compile problem that you
pointed out is from a code path that gets enabled with the
--enable-mmap-racache option. That particular option is experimental
and (as you have found) not well tested. I would not advise using it
in a production setting.
-Phil
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