Hi all, I've been investigating a problem with tests of our database processing jobs running on cephfs apparently reading several times more data than actually exists in the working set. I haven't had much luck diagnosing the cause so far, but one possibility I'd at least like to rule out is that the kernel cephfs client is discarding pages with cached reads too aggressively and so we're redundantly reading small chunks of data over and over again. Our access patterns are quite unusual -- we read small chunks (perhaps a few hundred kilobytes) from files, then close the file handles before reopening and doing more reads. I found a 10 year old thread indicating that cephfs would outright clear page caches for files in situations like this: https://ceph-users.ceph.narkive.com/o2vJ4rWf/cephfs-and-page-cache That behaviour was patched out long ago, but I'd like to know whether aggressive page cache eviction like this is still known to be an issue with certain access patterns, even if just to eliminate it as a possibility. We're hosting ceph on the same machines as our database which further makes me wonder if some kind of cache pressure could be involved. Regards, Domhnall *********************************************************************************************************************************************************************** This email, its contents and any files attached are a confidential communication and are intended only for the named addressees indicated in the message. If you are not the named addressee or if you have received this email in error, you may not, without the consent of KX, copy, use or rely on any information or attachments in any way. Please notify the sender by return email and delete it from your email system. Unless separately agreed, KX does not accept any responsibility for the accuracy or completeness of the contents of this email or its attachments. Please note that any views, opinion or advice contained in this communication are those of the sending individual and not those of KX and KX shall have no liability whatsoever in relation to this communication (or its content) unless separately agreed. ***********************************************************************************************************************************************************************