Bug 639795
| Summary: | Performance Tuning Guide: TRACKING BUG for [MEMORY] [VM Tuning] | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 6 | Reporter: | Don Domingo <ddomingo> |
| Component: | doc-Performance_Tuning_Guide | Assignee: | Laura Bailey <lbailey> |
| Status: | CLOSED NEXTRELEASE | QA Contact: | ecs-bugs |
| Severity: | medium | Docs Contact: | |
| Priority: | low | ||
| Version: | 6.2 | CC: | jskeoch, lwoodman |
| Target Milestone: | rc | Keywords: | Documentation, Tracking |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2011-10-31 01:07:42 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | |||
| Bug Blocks: | 639779 | ||
| Deadline: | 2011-07-22 | ||
ACK to the VM tuning chapter. Larry |
1.) NEEDINFO: pagecache RHEL6 does no have the /proc/sys/vm/pagecache tunable parameter. 2.) NEEDINFO: slabcache Not sure what this means, there is no slabcache file in the /proc filesystem. 3.) min_free_kbytes Be cautious when setting this parameter, as both too-low and too-high values can be damaging. Setting it to a value lower than 1024 KB results in a system that is prone to deadlock under high loads. A reason for this would be nice. However, setting this parameter to a value that is too high will cause your system to become out-of-memory immediately. I assume "too high" is "as much/more memory than your system has available". Setting min_free_kbytes too low will prevent the system from reclaiming memory all together. This can result in system hangs and/or OOM killing several processes. Too high is something like 5% - 10% of memory. Linux is designed to use all of the RAM to cache filesystem data, setting min_free_kbytes higher than that will cause the system to spend all of its time reclaiming memory. 4.) drop_caches Is this the right parameter to use with page cache and slab cache? The pagecache parameter doesn't seem to exist any more. /sys/proc/vm/drop_caches does exist in RHEL6. "echo 1 > /proc/sys/vm/drop_caches" will cause to the system to invalidate and free all pagecache memory. "echo 2 > /proc/sys/vm/drop_caches" will cause the system to free all unused slabcache memory. "echo 3 > /proc/sys/vm/drop_caches" cause the system to free both pagecache and slabcache memory. The use of /proc/sys/vm/slabcache should be limited to freeinf memory between benchmarking runs and should not be used in a production environment. Larry