1ec3b5fe6e
Right now, all new ZIP drivers are adapted to crypto_acomp APIs rather than legacy crypto_comp APIs. Tradiontal ZIP drivers like lz4,lzo etc have been also wrapped into acomp via scomp backend. But zswap.c is still using the old APIs. That means zswap won't be able to work on any new ZIP drivers in kernel. This patch moves to use cryto_acomp APIs to fix the disconnected bridge between new ZIP drivers and zswap. It is probably the first real user to use acomp but perhaps not a good example to demonstrate how multiple acomp requests can be executed in parallel in one acomp instance. frontswap is doing page load and store page by page synchronously. swap_writepage() depends on the completion of frontswap_store() to decide if it should call __swap_writepage() to swap to disk. However this patch creates multiple acomp instances, so multiple threads running on multiple different cpus can actually do (de)compression parallelly, leveraging the power of multiple ZIP hardware queues. This is also consistent with frontswap's page management model. The old zswap code uses atomic context and avoids the race conditions while shared resources like zswap_dstmem are accessed. Here since acomp can sleep, per-cpu mutex is used to replace preemption-disable. While it is possible to make mm/page_io.c and mm/frontswap.c support async (de)compression in some way, the entire design requires careful thinking and performance evaluation. For the first step, the base with fixed connection between ZIP drivers and zswap should be built. Link: https://lkml.kernel.org/r/20201107065332.26992-1-song.bao.hua@hisilicon.com Signed-off-by: Barry Song <song.bao.hua@hisilicon.com> Acked-by: Vitaly Wool <vitalywool@gmail.com> Cc: Luis Claudio R. Goncalves <lgoncalv@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: David S. Miller <davem@davemloft.net> Cc: Mahipal Challa <mahipalreddy2006@gmail.com> Cc: Seth Jennings <sjenning@redhat.com> Cc: Dan Streetman <ddstreet@ieee.org> Cc: Zhou Wang <wangzhou1@hisilicon.com> Cc: Colin Ian King <colin.king@canonical.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.