On Thursday, 21. July 2016 16:02:06 Vlastimil Babka wrote: > > recently we've updated our production mail server from 3.14.69 > > to 3.14.73 and it worked fine for a few days. When the box is really > > busy (=incoming malware via email), the I/O speed drops to crawl, > > I don't see anything either, might be some change e.g. under fs/ though. > How about git bisect? One day later I failed to trigger it, so no easy git bisect. Yesterday another busy mail server showed the same problem during backup creation. This time I knew about slabtop and could see that the ext4_inode_cache occupied about 393MB of the 776MB total low memory. Write speed was down to 25 MB/s. "sysctl -w vm.drop_caches=3" cleared the inode cache and the write speed was back to 300 MB/s. It might be related to memory fragmentation of low memory due to the inode cache, the mail server has over 1.400.000 millions files. I suspect the problem is unrelated to 3.14.73 per se, it seems to trigger depending how busy the machine is and the memory layout. A 64 bit kernel (even with a 32 bit userspace) is the proper solution here. Still that would mean to deprecate working 32 bit only boxes. Cheers, Thomas -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>