![]() | |||||||||||||
Messages in this thread |
Jon Smirl wrote: > On 5/25/06, Andrew Morton <akpm@osdl.org> wrote: > >> These are nice-looking numbers, but one wonders. If optimising >> readahead >> makes this much difference to postgresql performance then postgresql >> should >> be doing the readahead itself, rather than relying upon the kernel's >> ability to guess what the application will be doing in the future. >> Because >> surely the database can do a better job of that than the kernel. >> >> That would involve using posix_fadvise(POSIX_FADV_RANDOM) to disable >> kernel >> readahead and then using posix_fadvise(POSIX_FADV_WILLNEED) to launch >> application-level readahead. > > > Users have also reported that this patch fixes performance problems > from web servers using sendfile(). In the case of lighttpd they > actually stopped using sendfile() for large transfers and wrote a user > space replacement where they could control readahead manually. With > this patch in place sendfile() went back to being faster than the user > space implementation. Of course, that is something one would expect should be made to work properly with the current readahead implementation. I don't see Wu's patches getting in for a little while yet. Reproducable test cases (preferably without a whole lot of network clients) should get this proble fixed. -- Send instant messages to your online friends http://au.messenger.yahoo.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
| Last update: 2006-05-26 05:16 [from the cache] ©2003-2008 | |||||||||||||