[CC ext/jbd experts] On Wed 13-07-16 01:48:57, Houssem Daoud wrote: > Hi, > > I was testing the filesystem performance of my system using the following > script: > > #!/bin/bash > while true; > do > dd if=/dev/zero of=output.dat bs=100M count=1 > done > > I noticed that after some time, all the physical memory is consumed by the > LRU inactive list and only 120 MB are left to the system. > /proc/meminfo shows the following information: > MemTotal: 4021820 Kb > MemFree: 121912 Kb > Active: 1304396 Kb > Inactive: 2377124 Kb > > The evolution of memory utilization over time is available in this link: > http://secretaire.dorsal.polymtl.ca/~hdaoud/ext4_journal_meminfo.png > > With the help of a kernel tracer, I found that most of the pages in the > inactive list are created by the ext4 journal during a truncate operation. > The call stack of the allocation is: > [ > __alloc_pages_nodemask > alloc_pages_current > __page_cache_alloc > find_or_create_page > __getblk > jbd2_journal_get_descriptor_buffer > jbd2_journal_commit_transaction > kjournald2 > kthread > ] > > I can't find an explanation why the LRU is growing while we are just writing > to the same file again and again. I know that the philosophy of memory > management in Linux is to use the available memory as much as possible, but > what is the need of keeping truncated pages in the LRU if we know that they > are not even accessible ? > > Thanks ! > > ps: My system is running kernel 4.3 with ext4 filesystem (journal mode) > > -- > 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> -- Michal Hocko SUSE Labs -- 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>
