On Wed, Jan 28, 2004 at 01:38:29PM -0800, Mark Ferlatte wrote: [snip] > The problem (bug) is that block device IO has to go through buffers > that are below 1GB. The memory manager doesn't know this, so what > happens is that the IO layer requests a block of memory below 1GB, and > the swapout daemon (kswapd) then runs around like a madman trying to > free pages, instead of shuffling pages that don't need to be below 1GB > to higher memory addresses. Since many of the pages below 1GB can't > be freed (they belong to active programs), the IO starves. > > With 1GB of memory, both the IO layer and the swapout daemon are > working with the same view of memory, so the bug is concealed, and > performance is good. > > I have heard of people trying 2GB, and having it work, but it didn't > for me.
I was the poster who initiated the previous thread on this subject. The problem disappeared here after we went down to 2 GB of memory (although we physically removed it from the server rather than passing the arg to the kernel... shouldn't make a difference though, I'd imagine). We went straight from 4 GB to 2 GB, so I can't comment on the results of using 3 GB. Our problem didn't seem to directly correspond with the 1 GB threshold -- it wouldn't manifest itself until the server had allocated all 4 GB of RAM. After a reboot, it would be nice and speedy again for a day or two until all the memory was being used for buffering again. Dan -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
