os/bluestore: remove CephContext* from BmapEntry. #13651
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Each BmapEntry instance stores a pointer to the same CephContext. As we expect to have thousands of instances the overhead might be too high. For instance, serving 1 TiB SSD disk on x86-64, while using the default settings, results in 32 MiB of extra memory consumption: # assuming sizeof(unsigned long) * CHAR_BIT == 64 >>> 1024 * 1024 * 1024 * 1024 / 4096 / 64 4194304 >>> 4194304 * 8 / 1024 32768 Although memory is cheap, CPU's caches are not. Signed-off-by: Radoslaw Zarzynski <rzarzynski@mirantis.com>
liewegas
changed the title
liewegas
approved these changes
Feb 26, 2017
agent issue, retest this please. |
|
retest this please. |
ifed01
approved these changes
Feb 27, 2017
| @@ -123,8 +123,7 @@ void BmapEntry::_init_bit_mask() | |||
| BmapEntry::m_bit_mask_init = true; | |||
| } | |||
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| BmapEntry::BmapEntry(CephContext* cct, bool full) | |||
| : cct(cct) | |||
| BmapEntry::BmapEntry(CephContext*, const bool full) | |||
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Suggest to remove CephContext parameter...
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You're right. I deferred the clean-up to not introduce dependencies between patches as I'm going to touch BitMapZone as well. Having CephContext* there costs us additional 2 MiB in the case of 1 TiB SSD. :-(
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Each
BmapEntryinstance stores a pointer to the sameCephContext.As we expect to have thousands of instances the overhead might
be too high. For example, serving 1 TiB SSD disk on x86-64,
while using the default settings, results in 32 MiB of extra
memory consumption:
Although memory is cheap, CPU's caches are not.
Signed-off-by: Radoslaw Zarzynski rzarzynski@mirantis.com