€•O      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ//translations/zh_CN/locking/percpu-rw-semaphore”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ//translations/zh_TW/locking/percpu-rw-semaphore”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ//translations/it_IT/locking/percpu-rw-semaphore”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ//translations/ja_JP/locking/percpu-rw-semaphore”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ//translations/ko_KR/locking/percpu-rw-semaphore”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ//translations/sp_SP/locking/percpu-rw-semaphore”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒPercpu rw semaphores”h]”hŒPercpu rw semaphores”…””}”(hh¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒI/var/lib/git/docbuild/linux/Documentation/locking/percpu-rw-semaphore.rst”h KubhŒ	paragraph”“”)”}”(hŒdPercpu rw semaphores is a new read-write semaphore design that is
optimized for locking for reading.”h]”hŒdPercpu rw semaphores is a new read-write semaphore design that is
optimized for locking for reading.”…””}”(hh¹hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(hŒÞThe problem with traditional read-write semaphores is that when multiple
cores take the lock for reading, the cache line containing the semaphore
is bouncing between L1 caches of the cores, causing performance
degradation.”h]”hŒÞThe problem with traditional read-write semaphores is that when multiple
cores take the lock for reading, the cache line containing the semaphore
is bouncing between L1 caches of the cores, causing performance
degradation.”…””}”(hhÇhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(hŒìLocking for reading is very fast, it uses RCU and it avoids any atomic
instruction in the lock and unlock path. On the other hand, locking for
writing is very expensive, it calls synchronize_rcu() that can take
hundreds of milliseconds.”h]”hŒìLocking for reading is very fast, it uses RCU and it avoids any atomic
instruction in the lock and unlock path. On the other hand, locking for
writing is very expensive, it calls synchronize_rcu() that can take
hundreds of milliseconds.”…””}”(hhÕhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(hŒëThe lock is declared with "struct percpu_rw_semaphore" type.
The lock is initialized with percpu_init_rwsem, it returns 0 on success
and -ENOMEM on allocation failure.
The lock must be freed with percpu_free_rwsem to avoid memory leak.”h]”hŒïThe lock is declared with â€œstruct percpu_rw_semaphoreâ€ type.
The lock is initialized with percpu_init_rwsem, it returns 0 on success
and -ENOMEM on allocation failure.
The lock must be freed with percpu_free_rwsem to avoid memory leak.”…””}”(hhãhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(hŒxThe lock is locked for read with percpu_down_read, percpu_up_read and
for write with percpu_down_write, percpu_up_write.”h]”hŒxThe lock is locked for read with percpu_down_read, percpu_up_read and
for write with percpu_down_write, percpu_up_write.”…””}”(hhñhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(hŒ¢The idea of using RCU for optimized rw-lock was introduced by
Eric Dumazet <eric.dumazet@gmail.com>.
The code was written by Mikulas Patocka <mpatocka@redhat.com>”h]”(hŒLThe idea of using RCU for optimized rw-lock was introduced by
Eric Dumazet <”…””}”(hhÿhžhhŸNh NubhŒ	reference”“”)”}”(hŒeric.dumazet@gmail.com”h]”hŒeric.dumazet@gmail.com”…””}”(hj	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”Œmailto:eric.dumazet@gmail.com”uh1j  hhÿubhŒ,>.
The code was written by Mikulas Patocka <”…””}”(hhÿhžhhŸNh Nubj  )”}”(hŒmpatocka@redhat.com”h]”hŒmpatocka@redhat.com”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”Œmailto:mpatocka@redhat.com”uh1j  hhÿubhŒ>”…””}”(hhÿhžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubeh}”(h]”Œpercpu-rw-semaphores”ah ]”h"]”Œpercpu rw semaphores”ah$]”h&]”uh1h¡hhhžhhŸh¶h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h¶uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¦NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
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