From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brendan Higgins Subject: Re: [PATCH v9 03/18] kunit: test: add string_stream a std::stream like string builder Date: Tue, 16 Jul 2019 11:55:54 -0700 Message-ID: References: <20190712081744.87097-1-brendanhiggins@google.com> <20190712081744.87097-4-brendanhiggins@google.com> <20190715204356.4E3F92145D@mail.kernel.org> <20190715220407.0030420665@mail.kernel.org> <20190716153400.5CB182054F@mail.kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20190716153400.5CB182054F@mail.kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: Stephen Boyd Cc: Frank Rowand , Greg KH , Josh Poimboeuf , Kees Cook , Kieran Bingham , Luis Chamberlain , Peter Zijlstra , Rob Herring , shuah , Theodore Ts'o , Masahiro Yamada , devicetree , dri-devel , kunit-dev@googlegroups.com, "open list:DOCUMENTATION" , linux-fsdevel@vger.kernel.org, linux-kbuild , Linux Kernel Mailing List , open list:KERNEL SELFTEST FRAMEWORK List-Id: linux-nvdimm@lists.01.org On Tue, Jul 16, 2019 at 8:34 AM Stephen Boyd wrote: > > Quoting Brendan Higgins (2019-07-15 15:43:20) > > On Mon, Jul 15, 2019 at 3:11 PM Brendan Higgins > > wrote: > > > > > > On Mon, Jul 15, 2019 at 3:04 PM Stephen Boyd wrote: > > > > > > > > Quoting Brendan Higgins (2019-07-15 14:11:50) > > > > > On Mon, Jul 15, 2019 at 1:43 PM Stephen Boyd wrote: > > > > > > > > > > > > I also wonder if it would be better to just have a big slop buffer of a > > > > > > 4K page or something so that we almost never have to allocate anything > > > > > > with a string_stream and we can just rely on a reader consuming data > > > > > > while writers are writing. That might work out better, but I don't quite > > > > > > understand the use case for the string stream. > > > > > > > > > > That makes sense, but might that also waste memory since we will > > > > > almost never need that much memory? > > > > > > > > Why do we care? These are unit tests. > > > > > > Agreed. > > > > > > > Having allocations in here makes > > > > things more complicated, whereas it would be simpler to have a pointer > > > > and a spinlock operating on a chunk of memory that gets flushed out > > > > periodically. > > > > > > I am not so sure. I have to have the logic to allocate memory in some > > > case no matter what (what if I need more memory that my preallocated > > > chuck?). I think it is simpler to always request an allocation than to > > > only sometimes request an allocation. > > > > Another even simpler alternative might be to just allocate memory > > using kunit_kmalloc as we need it and just let the kunit_resource code > > handle cleaning it all up when the test case finishes. > > Sure, sounds like a nice way to avoid duplicating similar logic to > maintain a list of things to free later. I think I will go that route for now. > > > > What do you think? > > If you go the allocation route then you'll need to have the flags to > know what context you're in to allocate appropriately. Does that mean > all the string operations will now take GFP flags? We could set the GFP flags in the constructor, store them in a field, and then just reuse them. Thanks!