On Tue, Oct 23, 2018 at 08:26:40AM -0700, Matthew Wilcox wrote: > On Tue, Oct 23, 2018 at 09:02:56AM -0600, Shuah Khan wrote: > > Hi Michal, > > > > On 10/23/2018 01:23 AM, Michal Hocko wrote: > > > Hi Shuah, > > > > > > On Mon 22-10-18 18:52:53, Uladzislau Rezki wrote: > > >> On Mon, Oct 22, 2018 at 02:51:42PM +0200, Michal Hocko wrote: > > >>> Hi, > > >>> I haven't read through the implementation yet but I have say that I > > >>> really love this cover letter. It is clear on intetion, it covers design > > >>> from high level enough to start discussion and provides a very nice > > >>> testing coverage. Nice work! > > >>> > > >>> I also think that we need a better performing vmalloc implementation > > >>> long term because of the increasing number of kvmalloc users. > > >>> > > >>> I just have two mostly workflow specific comments. > > >>> > > >>>> A test-suite patch you can find here, it is based on 4.18 kernel. > > >>>> ftp://vps418301.ovh.net/incoming/0001-mm-vmalloc-stress-test-suite-v4.18.patch > > >>> > > >>> Can you fit this stress test into the standard self test machinery? > > >>> > > >> If you mean "tools/testing/selftests", then i can fit that as a kernel module. > > >> But not all the tests i can trigger from kernel module, because 3 of 8 tests > > >> use __vmalloc_node_range() function that is not marked as EXPORT_SYMBOL. > > > > > > Is there any way to conditionally export these internal symbols just for > > > kselftests? Or is there any other standard way how to test internal > > > functionality that is not exported to modules? > > > > > > > The way it can be handled is by adding a test module under lib. test_kmod, > > test_sysctl, test_user_copy etc. > > The problem is that said module can only invoke functions which are > exported using EXPORT_SYMBOL. And there's a cost to exporting them, > which I don't think we're willing to pay, purely to get test coverage. > > Based on my own experience with the IDA & XArray test suites, I would > like to propose a solution which does not require exporting all of > these symbols: > > Create a new kernel module in mm/test_vmalloc.c > > Towards the top of that file, > > #include <linux/export.h> > #undef EXPORT_SYMBOL > #define EXPORT_SYMBOL(x) /* */ > #include "vmalloc.c" > > Now you can invoke even static functions from your test harness. I see your point. But i also think that it would not be so easy to go. <snip> #undef CONFIG_HAVE_ARCH_HUGE_VMAP #undef CONFIG_PROC_FS #include "../hikey_linux.git/mm/vmalloc.c" #include <linux/random.h> <snip> <snip> LD [M] /mnt/coding/vmalloc_performance_test/vmalloc_test.o Building modules, stage 2. MODPOST 1 modules WARNING: "__pud_alloc" [/mnt/coding/vmalloc_performance_test/vmalloc_test.ko] undefined! WARNING: "__sync_icache_dcache" [/mnt/coding/vmalloc_performance_test/vmalloc_test.ko] undefined! WARNING: "warn_alloc" [/mnt/coding/vmalloc_performance_test/vmalloc_test.ko] undefined! WARNING: "pmd_clear_bad" [/mnt/coding/vmalloc_performance_test/vmalloc_test.ko] undefined! WARNING: "pgd_clear_bad" [/mnt/coding/vmalloc_performance_test/vmalloc_test.ko] undefined! WARNING: "swapper_pg_dir" [/mnt/coding/vmalloc_performance_test/vmalloc_test.ko] undefined! WARNING: "__pmd_alloc" [/mnt/coding/vmalloc_performance_test/vmalloc_test.ko] undefined! WARNING: "pud_clear_bad" [/mnt/coding/vmalloc_performance_test/vmalloc_test.ko] undefined! WARNING: "__pte_alloc_kernel" [/mnt/coding/vmalloc_performance_test/vmalloc_test.ko] undefined! LD [M] /mnt/coding/vmalloc_performance_test/vmalloc_test.ko <snip> i.e. i will need either link with objects where those functions are or wrap them up somehow. Thanks! -- Vlad Rezki
