Hi John,Thanks for reviewing! Since major questions are from this thread, so I think we can start from this.
On 2018年06月30日 06:47, John Ferlan wrote:
The cachetunes from Cache Allocation Technology(CAT) and memorytunes from Memory Bandwidth Allocation(MBA) are both features from Resource Directory Technology. RDT is a collection of resource distribution technology, right now it includes CAT and MBA. Details information can be found 17.18.1 of Intel's sdm.On 06/15/2018 05:29 AM, bing.niu@xxxxxxxxx wrote:From: Bing Niu <bing.niu@xxxxxxxxx> resctrl not only supports cache tuning, but also memory bandwidth tuning. Rename cachetune to restune(resource tuning) to reflect that. Signed-off-by: Bing Niu <bing.niu@xxxxxxxxx> --- src/conf/domain_conf.c | 44 ++++++++++++++++++++++---------------------- src/conf/domain_conf.h | 10 +++++----- src/qemu/qemu_process.c | 18 +++++++++--------- 3 files changed, 36 insertions(+), 36 deletions(-)Not so sure I'm liking [R|r]estune[s]... Still @cachetunes is an array of a structure that contains a vCPU bitmap and a virResctrlAllocPtr for the /cputune/cachetunes data. The virResctrlAllocPtr was changed to add a the bandwidth allocation, so does this really have to change?
https://software.intel.com/sites/default/files/managed/39/c5/325462-sdm-vol-1-2abcd-3abcd.pdfThe RDT capability and configuration methods is exposed to user land in form of resctrl file system by kernel. The basic programming model for this resctrl fs interface like this:
1. create a folder under /sys/fs/resctrl. And this folder is called one resctrl group.
2. writing user desired CAT and MBA config to the file /sys/fs/resctrl/<YOUR_GROUP_NAME>/schemata to allocate the cache or memory bandwidth. you can set CAT and MBA together or any of them.
3. moving the threads you want to that resctrl group by writing threads' PID to /sys/fs/resctrl/<YOUR_GROUP_NAME>/task file. So that those threads can be assign with the resource allocated in step 2. And those resources are shared by those threads.
*NOTE*: A thread only can be put in one resctrl group. This requirement is from how RDT and resctrl works. Each resctrl group has a closid. The resource configuration in above step2 is set to that closid's msr(IA32_L?_QoS) to describe the resource allocation for this closid. And thread use this closid to claim the allocated resource during context switch(scheduled_in()) in kernel by writing the closid to the msr IA32_PQR_ASSOC. With closid wrote in IA32_PQR_ASSOC, RDT hardware knows current running closid and allocated resource basing on this closid's IA32_L?_QoS msr.
That why a thread can be put into one restrcl group only. Details description of resctrl can be found: https://github.com/torvalds/linux/blob/v4.17/Documentation/x86/intel_rdt_ui.txt :)Basing on above information, my understanding is that virResctrlAllocPtr is not only bind to cachetunes. It should be a backing object to describe a resctrl group. Especially current virresctrl class already works as that. Libvirt will create one resctrl group for each virResctrlAllocPtr by virResctrlAllocCreate() interface.
So from components view, the big picture is something like below.
<memorytune ^cpus='0-3'>
+---------+
| <cachetune vcpus='0-3'>
XML | +
parser +-----------+
|
|
+------------------------------+
|
|
internal resctrl +------v--------------+
backing object | virResctrlAllocPtr |
+------+--------------+
|
|
+------------------------------+
|
+--v-------+
| |
| schemata |
/sys/fs/resctrl | tasks |
| . |
| . |
| |
+----------+
Does this make sense? :)
I think the question is - if both cachetunes and memtunes exist in
domain XML, then for which does the @vcpus relate to. That is, from the
cover there's:
<memorytune vcpus='0-1'>
<node id='0' bandwidth='20'/>
</memorytune>
and then there's a
<cachetune vcpus='0-3'>
<cache id='0' level='3' type='both' size='3' unit='MiB'/>
<cache id='1' level='3' type='both' size='3' unit='MiB'/>
</cachetune>
Now what? I haven't looked at patch 4 yet to even know how this "works".
I also raised this concern in the first round review. Ideally, if we can have a domain XML like this
<resourcetune vcpu='0-3'>
<memorytune>
<node id='0' bandwidth='20'/>
</memorytune>
<cachetune>
<cache id='0' level='3' type='both' size='3' unit='MiB'/>
<cache id='1' level='3' type='both' size='3' unit='MiB'/>
</cachetune>
<resourcetune>
That will be more clear. Above domain XML means: one resctrl group with
memory bandwidth 20 @node 0, L3 cache 3MB @ node0 and node 1. Put vcpu
'0-3' to this resctrl group. So those resources are shared among vcpus.
However, Pavel pointed out that we must keep backward compatible. And we
need keep <cachetune vcpus='0-3'>.
In RFC v1, I also proposed to put memory bandwidth into cachetunes section like:
<cachetune vcpus='0-3'>
<cache id='0' level='3' type='both' size='3' unit='MiB'/>
<node id='0' bandwidth='20'/>
<cachetune vcpus>
Maintainer also comments on this "it's not a clear XML definition",
describing memory bandwidth inside a cachetune section. That's why we
come with a separated memorytune section.
In your example, the current implement will stop creating resctrl group
and throw an error. vcpu list cannot overlap between memorytune and
cachetune, but they can be same. Since vcpu can be put into one resctrl
group only.
My understanding is that we can set using <resourcetune> to describe cachetune and memorytune together as a long term goal. Since that needs to deprecate cachetune's vcpu list. I am not sure about procedure to remove existing XML elements. Maybe you can point out. For the short term goal, we can use this separated <memorytune vcpus='0-1'> section. How do you think? :)
I think what you want to do is create a virDomainMemtuneDef that mimics virDomainCachetuneDef, but I'm not 100% sure. Of course that still leaves me wondering how much of virResctrlAllocPtr then becomes wasted. You chose an integration point, but essentially have separate technologies. I'm trying to make sense of it all and am starting to get lost in the process of doing that.
From resctrl group perspective, I don't think extend memory bandwidth information in virResctrlAllocPtr is a waste. I think this is a feature extending. :)
If @bandwidth can not be > 100... Can we duplicate the @id somehow? So
Something like
<cachetune vcpus='0-3'>
<cache id='0' level='3' type='both' size='3' unit='MiB'/>
<node id='0' bandwidth='20'/>
</cachetune>
or
<cachetune vcpus='0-3'>
<cache id='0' level='3' type='both' size='3' unit='MiB'
bandwidth='20'/>
</cachetune> ???That also works. This is something I did in RFC v1. But there is a comment said it's better not to mix memory bandwidth with cachetune. That may confuse people. :(
how does that free buffer that got 100% and then gets subtracted from really work in this model? I probably need to study the code some more, but it's not clear it requires using the "same" sort of logic that cachetune uses where there could be different types (instructs, data, or both) that would be drawing from the size, right? I think that's how that worked. So what's the corollary for memtunes? You set a range from 0 to 100, right and that's it. OK, too many questions and it's late so I'll stop here... Hopefully I didn't leave any stray thoughts in the review of patch 1 or 2.
The policy we used for memory bandwidth is consistent with the existing cachetune. Current cache allocation logic model forbids cache allocation overlap. This is to prevent resource contention I think. Same strategy on memory allocation part. Since total bandwidth beyond to 100 will lead to bandwidth competition.
Existing cache allocation logic achieves this by first populating virResctrlInfoPtr structure. Libvirt will fill the virResctrlInfoPtr structure during traverse host's cache hierarchy. When allocating cache by virResctrlAllocCreate, libvirt will first create a virResctrlAllocPtr basing on information from virResctrlInfoPtr. This virResctrlAllocPtr represents the maximum resource available(I mean no any allocation previously). Then libvirt traverse all resctrl groups (in /sys/fs/resctrl/)created already, subtract the resource they claimed. So the left resource is the resource free. Libvirt compares this free resource with resource requested in virResctrlAllocCreate. If enough free resource available, then new resctrl group will be created. Memory bandwidth part follows the same idea, only the difference is memory bandwidth use percentage number and cache use bitmap.
Bing
Johndiff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c index 62c412e..b3543f3 100644 --- a/src/conf/domain_conf.c +++ b/src/conf/domain_conf.c @@ -2950,14 +2950,14 @@ virDomainLoaderDefFree(virDomainLoaderDefPtr loader)static void-virDomainCachetuneDefFree(virDomainCachetuneDefPtr cachetune) +virDomainRestuneDefFree(virDomainRestuneDefPtr restune) { - if (!cachetune) + if (!restune) return;- virObjectUnref(cachetune->alloc);- virBitmapFree(cachetune->vcpus); - VIR_FREE(cachetune); + virObjectUnref(restune->alloc); + virBitmapFree(restune->vcpus); + VIR_FREE(restune); }@@ -3147,9 +3147,9 @@ void virDomainDefFree(virDomainDefPtr def)virDomainShmemDefFree(def->shmems[i]); VIR_FREE(def->shmems);- for (i = 0; i < def->ncachetunes; i++)- virDomainCachetuneDefFree(def->cachetunes[i]); - VIR_FREE(def->cachetunes); + for (i = 0; i < def->nrestunes; i++) + virDomainRestuneDefFree(def->restunes[i]); + VIR_FREE(def->restunes);VIR_FREE(def->keywrap); @@ -18971,7 +18971,7 @@ virDomainCachetuneDefParse(virDomainDefPtr def,xmlNodePtr *nodes = NULL; virBitmapPtr vcpus = NULL; virResctrlAllocPtr alloc = virResctrlAllocNew(); - virDomainCachetuneDefPtr tmp_cachetune = NULL; + virDomainRestuneDefPtr tmp_restune = NULL; char *tmp = NULL; char *vcpus_str = NULL; char *alloc_id = NULL; @@ -18984,7 +18984,7 @@ virDomainCachetuneDefParse(virDomainDefPtr def, if (!alloc) goto cleanup;- if (VIR_ALLOC(tmp_cachetune) < 0)+ if (VIR_ALLOC(tmp_restune) < 0) goto cleanup;vcpus_str = virXMLPropString(node, "vcpus");@@ -19025,8 +19025,8 @@ virDomainCachetuneDefParse(virDomainDefPtr def, goto cleanup; }- for (i = 0; i < def->ncachetunes; i++) {- if (virBitmapOverlaps(def->cachetunes[i]->vcpus, vcpus)) { + for (i = 0; i < def->nrestunes; i++) { + if (virBitmapOverlaps(def->restunes[i]->vcpus, vcpus)) { virReportError(VIR_ERR_XML_ERROR, "%s", _("Overlapping vcpus in cachetunes")); goto cleanup; @@ -19056,16 +19056,16 @@ virDomainCachetuneDefParse(virDomainDefPtr def, if (virResctrlAllocSetID(alloc, alloc_id) < 0) goto cleanup;- VIR_STEAL_PTR(tmp_cachetune->vcpus, vcpus);- VIR_STEAL_PTR(tmp_cachetune->alloc, alloc); + VIR_STEAL_PTR(tmp_restune->vcpus, vcpus); + VIR_STEAL_PTR(tmp_restune->alloc, alloc);- if (VIR_APPEND_ELEMENT(def->cachetunes, def->ncachetunes, tmp_cachetune) < 0)+ if (VIR_APPEND_ELEMENT(def->restunes, def->nrestunes, tmp_restune) < 0) goto cleanup;ret = 0;cleanup: ctxt->node = oldnode; - virDomainCachetuneDefFree(tmp_cachetune); + virDomainRestuneDefFree(tmp_restune); virObjectUnref(alloc); virBitmapFree(vcpus); VIR_FREE(alloc_id); @@ -26874,7 +26874,7 @@ virDomainCachetuneDefFormatHelper(unsigned int level,static intvirDomainCachetuneDefFormat(virBufferPtr buf, - virDomainCachetuneDefPtr cachetune, + virDomainRestuneDefPtr restune, unsigned int flags) { virBuffer childrenBuf = VIR_BUFFER_INITIALIZER; @@ -26882,7 +26882,7 @@ virDomainCachetuneDefFormat(virBufferPtr buf, int ret = -1;virBufferSetChildIndent(&childrenBuf, buf);- virResctrlAllocForeachCache(cachetune->alloc, + virResctrlAllocForeachCache(restune->alloc, virDomainCachetuneDefFormatHelper, &childrenBuf);@@ -26895,14 +26895,14 @@ virDomainCachetuneDefFormat(virBufferPtr buf,goto cleanup; }- vcpus = virBitmapFormat(cachetune->vcpus);+ vcpus = virBitmapFormat(restune->vcpus); if (!vcpus) goto cleanup;virBufferAsprintf(buf, "<cachetune vcpus='%s'", vcpus); if (!(flags & VIR_DOMAIN_DEF_FORMAT_INACTIVE)) {- const char *alloc_id = virResctrlAllocGetID(cachetune->alloc); + const char *alloc_id = virResctrlAllocGetID(restune->alloc); if (!alloc_id) goto cleanup;@@ -27023,8 +27023,8 @@ virDomainCputuneDefFormat(virBufferPtr buf,def->iothreadids[i]->iothread_id); }- for (i = 0; i < def->ncachetunes; i++)- virDomainCachetuneDefFormat(&childrenBuf, def->cachetunes[i], flags); + for (i = 0; i < def->nrestunes; i++) + virDomainCachetuneDefFormat(&childrenBuf, def->restunes[i], flags);if (virBufferCheckError(&childrenBuf) < 0)return -1; diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h index 6344c02..9e71a0b 100644 --- a/src/conf/domain_conf.h +++ b/src/conf/domain_conf.h @@ -2228,10 +2228,10 @@ struct _virDomainCputune { };-typedef struct _virDomainCachetuneDef virDomainCachetuneDef;-typedef virDomainCachetuneDef *virDomainCachetuneDefPtr; +typedef struct _virDomainRestuneDef virDomainRestuneDef; +typedef virDomainRestuneDef *virDomainRestuneDefPtr;-struct _virDomainCachetuneDef {+struct _virDomainRestuneDef { virBitmapPtr vcpus; virResctrlAllocPtr alloc; }; @@ -2409,8 +2409,8 @@ struct _virDomainDef {virDomainCputune cputune; - virDomainCachetuneDefPtr *cachetunes;- size_t ncachetunes; + virDomainRestuneDefPtr *restunes; + size_t nrestunes;virDomainNumaPtr numa;virDomainResourceDefPtr resource; diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c index 93fd6ba..0659c06 100644 --- a/src/qemu/qemu_process.c +++ b/src/qemu/qemu_process.c @@ -2447,7 +2447,7 @@ qemuProcessResctrlCreate(virQEMUDriverPtr driver, virCapsPtr caps = NULL; qemuDomainObjPrivatePtr priv = vm->privateData;- if (!vm->def->ncachetunes)+ if (!vm->def->nrestunes) return 0;/* Force capability refresh since resctrl info can change@@ -2456,9 +2456,9 @@ qemuProcessResctrlCreate(virQEMUDriverPtr driver, if (!caps) return -1;- for (i = 0; i < vm->def->ncachetunes; i++) {+ for (i = 0; i < vm->def->nrestunes; i++) { if (virResctrlAllocCreate(caps->host.resctrl, - vm->def->cachetunes[i]->alloc, + vm->def->restunes[i]->alloc, priv->machineName) < 0) goto cleanup; } @@ -5259,8 +5259,8 @@ qemuProcessSetupVcpu(virDomainObjPtr vm, &vcpu->sched) < 0) return -1;- for (i = 0; i < vm->def->ncachetunes; i++) {- virDomainCachetuneDefPtr ct = vm->def->cachetunes[i]; + for (i = 0; i < vm->def->nrestunes; i++) { + virDomainRestuneDefPtr ct = vm->def->restunes[i];if (virBitmapIsBitSet(ct->vcpus, vcpuid)) {if (virResctrlAllocAddPID(ct->alloc, vcpupid) < 0) @@ -6955,8 +6955,8 @@ void qemuProcessStop(virQEMUDriverPtr driver, /* Remove resctrl allocation after cgroups are cleaned up which makes it * kind of safer (although removing the allocation should work even with * pids in tasks file */ - for (i = 0; i < vm->def->ncachetunes; i++) - virResctrlAllocRemove(vm->def->cachetunes[i]->alloc); + for (i = 0; i < vm->def->nrestunes; i++) + virResctrlAllocRemove(vm->def->restunes[i]->alloc);qemuProcessRemoveDomainStatus(driver, vm); @@ -7676,8 +7676,8 @@ qemuProcessReconnect(void *opaque)if (qemuConnectAgent(driver, obj) < 0) goto error;- for (i = 0; i < obj->def->ncachetunes; i++) {- if (virResctrlAllocDeterminePath(obj->def->cachetunes[i]->alloc, + for (i = 0; i < obj->def->nrestunes; i++) { + if (virResctrlAllocDeterminePath(obj->def->restunes[i]->alloc, priv->machineName) < 0) goto error; }-- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
-- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
