Ming Zhang <mingz@xxxxxxxxxxx> writes: > On Thu, 2005-07-14 at 19:29 -0400, Mark Hahn wrote: >> >> > i also want a way to clear part of the whole page cache by file id. :) >> >> understandably, kernel developers are don't high-prioritize this sort of >> not-useful-for-normal-work feature. > agree. Clearing just part of the page cache sounds too complicated to be worth it, but clearing it all seems reasonable; some kernel developers spend time doing benchmarks too! >> > Dan Christensen wrote: >> > >> > > I'm really surprised there isn't something in /proc you can use to >> > > clear or disable the cache. Would be very useful for benchmarking! >> >> I assume you noticed "blockdev --flushbufs", no? it works for me I had tried this and noticed that it didn't work for files on a filesystem. But it does seem to work for block devices. That's great, thanks. I didn't realize the cache was so complicated; it can be retained for files but not for the block device underlying those files! > a test i did show that even you have sda and sdb to form a raid0, > the page cache for sda and sdb will not be used by raid0. kind of > funny. I thought I had noticed raid devices making use of cache from underlying devices, but a test I just did agrees with your result, for both RAID-1 and RAID-5. Again, this seems odd. Shouldn't the raid layer take advantage of a block that's already in RAM? I guess this won't matter in practice, since you usually don't read from both a raid device and an underlying device. Dan - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
