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fix comments / add BACKPRESSURE_READS compile time option

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git-svn-id: svn+ssh://svn.corp.yahoo.com/yahoo/yrl/labs/pnuts/code/logstore@3773 8dad8b1f-cf64-0410-95b6-bcf113ffbcfe
This commit is contained in:
sears 2012-02-22 22:53:01 +00:00
parent 0b1d9dd236
commit fe07048ba3
1 changed files with 20 additions and 2 deletions
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22
logstore.cpp
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@ -27,6 +27,9 @@
#include <stasis/logger/filePool.h>
#include "mergeStats.h"
// Backpressure reads to avoid merge starvation? Experimental/short-term hack
//#define BACKPRESSURE_READS
static inline double tv_to_double(struct timeval tv)
{
return static_cast<double>(tv.tv_sec) +
@ -276,7 +279,13 @@ void logtable::flushTable()
datatuple * logtable::findTuple(int xid, const datatuple::key_t key, size_t keySize)
{
//prepare a search tuple
// Apply proportional backpressure to reads as well as writes. This prevents
// starvation of the merge threads on fast boxes.
#ifdef BACKPRESSURE_READS
merge_mgr->tick(merge_mgr->get_merge_stats(0));
#endif
//prepare a search tuple
datatuple *search_tuple = datatuple::create(key, keySize);
@ -456,6 +465,12 @@ datatuple * logtable::findTuple(int xid, const datatuple::key_t key, size_t keyS
**/
datatuple * logtable::findTuple_first(int xid, datatuple::key_t key, size_t keySize)
{
// Apply proportional backpressure to reads as well as writes. This prevents
// starvation of the merge threads on fast boxes.
#ifdef BACKPRESSURE_READS
merge_mgr->tick(merge_mgr->get_merge_stats(0));
#endif
//prepare a search tuple
datatuple * search_tuple = datatuple::create(key, keySize);
@ -637,7 +652,10 @@ void logtable::insertTuple(datatuple *tuple)
batch_size = 0;
}
}
merge_mgr->read_tuple_from_small_component(0, tuple); // has to be before rb_mut, since it calls tick with block = true, and that releases header_mut.
// Note, this is where we block for backpressure. Do this without holding
// any locks!
merge_mgr->read_tuple_from_small_component(0, tuple);
datatuple * pre_t = 0; // this is a pointer to any data tuples that we'll be deleting below. We need to update the merge_mgr statistics with it, but have to do so outside of the rb_mut region.
pre_t = insertTupleHelper(tuple);