> Subject: Re: [PATCH 8/8] mm/zswap: Use local lock to protect per-CPU data > > On 2020-05-20 11:13:31 [+0000], Song Bao Hua wrote: > > For example, on cpu1, once you begin to compress, you hold the percpu > acomp-ctx and percpu destination buffer of CPU1, the below code makes sure > you get the acomp and dstmem from the same core by disabling preemption > with get_cpu_var and put_cpu_var: > > dst = get_cpu_var(zswap_dstmem); > > acomp_ctx = *this_cpu_ptr(entry->pool->acomp_ctx); > > put_cpu_var(zswap_dstmem); > > > > then there are two cases: > > > > 1. after getting dst and acomp_ctx of cpu1, you might always work in cpu1, > the mutex in per-cpu acomp-ctx will guarantee two compressions won't do at > the same core in parallel, and it also makes certain compression and > decompression won't do at the same core in parallel. Everything is like before. > > For readability I suggest not to mix per-CPU and per-CTX variables like that. If > zswap_dstmem is protected by the mutex, please make it part of acomp_ctx. > Yep. it seems this will avoid the further explanations to more people who will read the code :-) > Sebastian Barry
