Messages in this thread | | | Date | Mon, 28 Nov 2022 11:29:48 -0500 | Subject | Re: [PATCH v2 2/2] module: Merge same-name module load requests | From | Prarit Bhargava <> |
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On 11/14/22 10:45, David Hildenbrand wrote: > On 14.11.22 16:38, Luis Chamberlain wrote: >> On Mon, Nov 14, 2022 at 09:57:56AM +0100, David Hildenbrand wrote: >>> On 12.11.22 02:47, Luis Chamberlain wrote: >>>> On Wed, Oct 19, 2022 at 02:00:55PM +0200, Petr Pavlu wrote: >>>>> On 10/18/22 20:33, Luis Chamberlain wrote: >>>>>> On Sat, Oct 15, 2022 at 11:27:10AM +0200, Petr Pavlu wrote: >>>>>>> The patch does address a regression observed after commit >>>>>>> 6e6de3dee51a >>>>>>> ("kernel/module.c: Only return -EEXIST for modules that have >>>>>>> finished >>>>>>> loading"). I guess it can have a Fixes tag added to the patch. >>>>>>> >>>>>>> I think it is hard to split this patch into parts because the >>>>>>> implemented >>>>>>> "optimization" is the fix. >>>>>> >>>>>> git describe --contains 6e6de3dee51a >>>>>> v5.3-rc1~38^2~6 >>>>>> >>>>>> I'm a bit torn about this situation. Reverting 6e6de3dee51a would >>>>>> be the >>>>>> right thing to do, but without it, it still leaves the issue reported >>>>>> by Prarit Bhargava. We need a way to resolve the issue on stable and >>>>>> then your optimizations can be applied on top. >>>>> >>>>> Simpler could be to do the following: >>>>> >>>>> diff --git a/kernel/module/main.c b/kernel/module/main.c >>>>> index d02d39c7174e..0302ac387e93 100644 >>>>> --- a/kernel/module/main.c >>>>> +++ b/kernel/module/main.c >>>>> @@ -2386,7 +2386,8 @@ static bool finished_loading(const char *name) >>>>> sched_annotate_sleep(); >>>>> mutex_lock(&module_mutex); >>>>> mod = find_module_all(name, strlen(name), true); >>>>> - ret = !mod || mod->state == MODULE_STATE_LIVE; >>>>> + ret = !mod || mod->state == MODULE_STATE_LIVE >>>>> + || mod->state == MODULE_STATE_GOING; >>>>> mutex_unlock(&module_mutex); >>>>> return ret; >>>>> @@ -2566,7 +2567,8 @@ static int add_unformed_module(struct module >>>>> *mod) >>>>> mutex_lock(&module_mutex); >>>>> old = find_module_all(mod->name, strlen(mod->name), true); >>>>> if (old != NULL) { >>>>> - if (old->state != MODULE_STATE_LIVE) { >>>>> + if (old->state == MODULE_STATE_COMING >>>>> + || old->state == MODULE_STATE_UNFORMED) { >>>>> /* Wait in case it fails to load. */ >>>>> mutex_unlock(&module_mutex); >>>>> err = wait_event_interruptible(module_wq, >>>>> @@ -2575,7 +2577,7 @@ static int add_unformed_module(struct module >>>>> *mod) >>>>> goto out_unlocked; >>>>> goto again; >>>>> } >>>>> - err = -EEXIST; >>>>> + err = old->state != MODULE_STATE_LIVE ? -EBUSY : -EEXIST; >>>>> goto out; >>>>> } >>>>> mod_update_bounds(mod); >>>> >>>> >>>> Prarit, can you verify this still does not break the issue you >>>> reported? >>>> David, does this also fix your issue? >>> >>> I didn't try, but from a quick glimpse I assume no. Allocating module >>> space >>> happens before handling eventual duplicates right now, before a >>> module even >>> is "alive" and in the MODULE_STATE_UNFORMED state. >> >> The first two hunks are a revert of commit 6e6de3dee51a and I'm under >> the impression that cauased your issues as *more* modules states are >> allowed through. >> >> The last hunk tries to fix what 6e6de3dee51a wanted to do. >> > > Note that I don't think the issue I raised is due to 6e6de3dee51a. > >>> But maybe I am missing something important. >> >> Please do test if you can. > > I don't have the machine at hand right now. But, again, I doubt this > will fix it. > > > The flow is in load_module(): > > mod = layout_and_allocate(info, flags); > if (IS_ERR(mod)) { > ... > } > > audit_log_kern_module(mod->name); > > /* Reserve our place in the list. */ > err = add_unformed_module(mod); > if (err) > goto free_module; > > > You can have 400 threads in layout_and_allocate() loading the same > module at the same time and running out of module space. Any changes to > add_unformed_module() and finished_loading() won't change that, because > they are not involved before the module space allocations happened. >
I'd like to see a refreshed patch but I tested the latest version and see that the boot time is LONGER with the change
Before:
[11:17 AM root@intel-eaglestream-spr-15 kernel-ark]# systemd-analyze Startup finished in 55.418s (firmware) + 22.766s (loader) + 35.856s (kernel) + 5.830s (initrd) + 15.671s (userspace) = 2min 15.542s multi-user.target reached after 15.606s in userspace.
After:
Startup finished in 55.314s (firmware) + 23.033s (loader) + 35.331s (kernel) + 5.176s (initrd) + 23.465s (userspace) = 2min 22.320s multi-user.target reached after 23.093s in userspace.
Subsequent reboots also indicate that userspace boot time is longer after the change.
P.
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