"Alex Ng (LIS)" <alexng@xxxxxxxxxxxxx> writes: >> -----Original Message----- >> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx] >> Sent: Friday, August 5, 2016 3:49 AM >> To: devel@xxxxxxxxxxxxxxxxxxxxxx >> Cc: linux-kernel@xxxxxxxxxxxxxxx; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; KY >> Srinivasan <kys@xxxxxxxxxxxxx>; Alex Ng (LIS) <alexng@xxxxxxxxxxxxx> >> Subject: [PATCH 3/4] Drivers: hv: balloon: get rid on ol_waitevent >> >> With the recently introduced in-kernel memory onlining >> (MEMORY_HOTPLUG_DEFAULT_ONLINE) these it no point in waiting for pages >> to come online in the driver and in case the feature is disabled the 5 >> second wait won't help. Get rid of the waiting. >> > > Continuing our internal discussion here. Here's the context. > >> > Is it necessary to remove the ol_waitevent in "Drivers: hv: balloon: get rid >> > on ol_waitevent"? If we respond to the host too quickly, then the next >> > hot-add request may not see the new pages come online and could fail to >> > alloc memory as seen in the call trace. >> > >> > Thoughts? >> >> This should not be an issue with CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE: we >> online pages when we add them (add_memory()) so when we reply to the host >> these pages are already online. But in case the onlining is done by an >> external tool (e.g. udev) this wait helps (not always, as if someone eats >> all memory before the next add_memory call we're still in trouble). > > MEMORY_HOTPLUG_DEFAULT_ONLINE is disabled in Kconfig by default. > Would it make sense to keep the wait and only #ifdef it out when CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE is set? I have a better idea. We can check 'memhp_auto_online' value to see the current status and don't wait if it is 'true'. Will do v2. -- Vitaly _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
