Bug 199169
| Summary: | [patch] zone "UMA Zones" has bigger size than need | ||||||
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| Product: | Base System | Reporter: | luke.tw | ||||
| Component: | kern | Assignee: | Dmitry Chagin <dchagin> | ||||
| Status: | Closed FIXED | ||||||
| Severity: | Affects Only Me | CC: | dchagin | ||||
| Priority: | --- | Keywords: | patch | ||||
| Version: | CURRENT | ||||||
| Hardware: | Any | ||||||
| OS: | Any | ||||||
| Attachments: |
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hm, mp_maxid is a max cpu id. on my 8 threaded cpu mp_maxid is 7. hi, Dmitry,
Thanks for your feedback.
That's right, but there is already one uma_cache in the struct uma_zone.
Let me do an experiment on sleepq_zone.
I have 4-core cpu and the mp_maxid is 3.
(kgdb) p mp_maxid
$1 = 3
The size of all per-cpu cache in sleepq_zone is 640 bytes.
(kgdb) p sleepq_zone
$2 = 0xfffff80002bb8000
(kgdb) p sleepq_zone->uz_cpu
$3 = 0xfffff80002bb8200
(kgdb) p masterzone_z->uz_size - (0xfffff80002bb8200 - 0xfffff80002bb8000)
$4 = 640
So, there are total 5 elements in the uz_cpu array
(kgdb) p 640 / sizeof(struct uma_cache)
$5 = 5
Only the first 4 elements are used.
(kgdb) p sleepq_zone->uz_cpu[0]
$6 = {uc_freebucket = 0x0, uc_allocbucket = 0xfffff80002bb1c00, uc_allocs = 73, uc_frees = 0}
(kgdb) p sleepq_zone->uz_cpu[1]
$7 = {uc_freebucket = 0x0, uc_allocbucket = 0xfffff8000516a800, uc_allocs = 18, uc_frees = 0}
(kgdb) p sleepq_zone->uz_cpu[2]
$8 = {uc_freebucket = 0x0, uc_allocbucket = 0xfffff80004747c00, uc_allocs = 18, uc_frees = 0}
(kgdb) p sleepq_zone->uz_cpu[3]
$9 = {uc_freebucket = 0x0, uc_allocbucket = 0xfffff800047a1c00, uc_allocs = 36, uc_frees = 0}
(kgdb) p sleepq_zone->uz_cpu[4]
$10 = {uc_freebucket = 0x0, uc_allocbucket = 0x0, uc_allocs = 0, uc_frees = 0}
(In reply to luke.tw from comment #2) Yes, I see. It would be nice to add db_show_zone DDB method and use a now unused uma_print_zone with their counterparts. A commit references this bug: Author: dchagin Date: Mon Apr 6 18:45:42 UTC 2015 New revision: 281162 URL: https://svnweb.freebsd.org/changeset/base/281162 Log: Properly calculate "UMA Zones" per cpu cache size. Avoid allocating an extra struct uma_cache since the struct uma_zone already has one. PR: 199169 Submitted by: luke.tw gmail com MFC after: 1 week Changes: head/sys/vm/uma_core.c A commit references this bug: Author: dchagin Date: Wed Apr 15 05:13:42 UTC 2015 New revision: 281543 URL: https://svnweb.freebsd.org/changeset/base/281543 Log: MFC r281162, r281451: Use flexible array for per cpu uma_cache to avoid allocating an extra struct uma_cache. PR: 199169 Changes: _U stable/10/ stable/10/sys/vm/uma_int.h committed, thanks. |
Created attachment 155194 [details] UMA Zones size patch It calculates the size for per cpu cache with (mp_maxid + 1 ). This allocates space with one extra struct uma_cache. * before patch % vmstat -z | grep Zone UMA Zones: 1152, 0, 196, 2, 196, 0, 0 * after patch % vmstat -z | grep Zone UMA Zones: 1024, 0, 196, 2, 196, 0, 0