Eric Dumazet wrote:
Hi
Browsing (and using) the excellent RCU infrastructure for files that
was adopted for 2.6.14-rc1, I noticed that the file_lock spinlock sit
close to mostly read fields of 'struct files_struct'
In SMP (and NUMA) environnements, each time a thread wants to open or
close a file, it has to acquire the spinlock, thus invalidating the
cache line containing this spinlock on other CPUS. So other threads
doing read()/write()/... calls that use RCU to access the file table
are going to ask further memory (possibly NUMA) transactions to read
again this memory line.
Please consider applying this patch. It moves the spinlock to another
cache line, so that concurrent threads can share the cache line
containing 'count' and 'fdt' fields.
How was the performance impact of this change measured?
Thanx...
ps
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