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SubjectSOLVED: Performance drop 2.6.0-test7 -> 2.6.1-rc2
Jan Kasprzak wrote:
: Yesterday I have upgraded the kernel on my FTP server to 2.6.1-rc2
: (from 2.6.0-test7) and today I have found the server struggling under
: load average of 40+ and the system was barely usable. The main load on the
: server is ProFTPd serving mainly ISO 9660 images using sendfile().

For archives: Andrew Morton suggested to apply the following patch
to mm/filemap.c (which in fact reverts part of the patch-2.6.1), and this
solved the problem (bigger-than-needed read ahead when doing sendfile()
of large files). 2.6.1 with this patch works for me now. Thanks!

-Yenya

diff -puN mm/filemap.c~readahead-partial-backout mm/filemap.c
--- 25/mm/filemap.c~readahead-partial-backout 2004-01-09 22:19:32.000000000 -0800
+++ 25-akpm/mm/filemap.c 2004-01-09 22:19:32.000000000 -0800
@@ -587,22 +587,13 @@ void do_generic_mapping_read(struct addr
read_actor_t actor)
{
struct inode *inode = mapping->host;
- unsigned long index, offset, last;
+ unsigned long index, offset;
struct page *cached_page;
int error;

cached_page = NULL;
index = *ppos >> PAGE_CACHE_SHIFT;
offset = *ppos & ~PAGE_CACHE_MASK;
- last = (*ppos + desc->count) >> PAGE_CACHE_SHIFT;
-
- /*
- * Let the readahead logic know upfront about all
- * the pages we'll need to satisfy this request
- */
- for (; index < last; index++)
- page_cache_readahead(mapping, ra, filp, index);
- index = *ppos >> PAGE_CACHE_SHIFT;

for (;;) {
struct page *page;
@@ -621,6 +612,7 @@ void do_generic_mapping_read(struct addr
}

cond_resched();
+ page_cache_readahead(mapping, ra, filp, index);

nr = nr - offset;
find_page:
_

--
| Jan "Yenya" Kasprzak <kas at {fi.muni.cz - work | yenya.net - private}> |
| GPG: ID 1024/D3498839 Fingerprint 0D99A7FB206605D7 8B35FCDE05B18A5E |
| http://www.fi.muni.cz/~kas/ Czech Linux Homepage: http://www.linux.cz/ |
| I actually have a lot of admiration and respect for the PATA knowledge |
| embedded in drivers/ide. But I would never call it pretty:) -Jeff Garzik |
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