Messages in this thread Patch in this message | | | From | Reinette Chatre <> | Subject | [RFC PATCH 3/7] x86/intel_rdt: Enable user to trigger pseudo-locked region restore | Date | Tue, 24 Jul 2018 13:40:14 -0700 |
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Expose a new debugfs file that user can use to trigger the restoration of a specific Cache Pseudo-Locked region at any time.
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> --- Documentation/x86/intel_rdt_ui.txt | 18 ++++++--- arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c | 45 ++++++++++++++++++++- 2 files changed, 56 insertions(+), 7 deletions(-)
diff --git a/Documentation/x86/intel_rdt_ui.txt b/Documentation/x86/intel_rdt_ui.txt index f662d3c530e5..4b124a54eee3 100644 --- a/Documentation/x86/intel_rdt_ui.txt +++ b/Documentation/x86/intel_rdt_ui.txt @@ -507,6 +507,17 @@ Cache Pseudo-Locking Debugging Interface The pseudo-locking debugging interface is enabled by default (if CONFIG_DEBUG_FS is enabled) and can be found in /sys/kernel/debug/resctrl. +The debugging interface supports the restoration and measurement of the cache +pseudo-locked region. When a pseudo-locked region is created a new debugfs +directory is created for it in debugfs as /sys/kernel/debug/resctrl/<newdir>. +Two write-only files, pseudo_lock_measure and pseudo_lock_restore, are present +in this directory. + +A Cache Pseudo-Locked region can be restored by writing one of 'Yy1' or 'on' +to pseudo_lock_restore. This would be needed if it is found that the memory +has been evicted from the cache and will result in the memory being +pseudo-locked to the original cache region. + There is no explicit way for the kernel to test if a provided memory location is present in the cache. The pseudo-locking debugging interface uses the tracing infrastructure to provide two ways to measure cache residency of @@ -525,11 +536,8 @@ the pseudo-locked region: the system, if any other measurements are in progress the counters and their corresponding event registers will be clobbered. -When a pseudo-locked region is created a new debugfs directory is created for -it in debugfs as /sys/kernel/debug/resctrl/<newdir>. A single -write-only file, pseudo_lock_measure, is present in this directory. The -measurement on the pseudo-locked region depends on the number, 1 or 2, -written to this debugfs file. Since the measurements are recorded with the +The measurement on the pseudo-locked region depends on the number, 1 or 2, +written to pseudo_lock_measure. Since the measurements are recorded with the tracing infrastructure the relevant tracepoints need to be enabled before the measurement is triggered. diff --git a/arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c b/arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c index 693f99594e9f..246cff17ce66 100644 --- a/arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c +++ b/arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c @@ -1290,7 +1290,7 @@ static int _pseudo_lock_restore(struct rdtgroup *rdtgrp) return ret; } -static int __attribute__ ((unused)) pseudo_lock_restore(struct rdtgroup *rdtgrp) +static int pseudo_lock_restore(struct rdtgroup *rdtgrp) { int ret; @@ -1302,6 +1302,43 @@ static int __attribute__ ((unused)) pseudo_lock_restore(struct rdtgroup *rdtgrp) return ret; } +static ssize_t pseudo_lock_restore_trigger(struct file *file, + const char __user *user_buf, + size_t count, loff_t *ppos) +{ + struct rdtgroup *rdtgrp = file->private_data; + size_t buf_size; + char buf[32]; + int ret; + bool bv; + + buf_size = min(count, (sizeof(buf) - 1)); + if (copy_from_user(buf, user_buf, buf_size)) + return -EFAULT; + + buf[buf_size] = '\0'; + ret = strtobool(buf, &bv); + if (ret == 0 && bv) { + ret = debugfs_file_get(file->f_path.dentry); + if (ret) + return ret; + ret = pseudo_lock_restore(rdtgrp); + if (ret == 0) + ret = count; + debugfs_file_put(file->f_path.dentry); + } else { + ret = -EINVAL; + } + + return ret; +} + +static const struct file_operations pseudo_restore_fops = { + .write = pseudo_lock_restore_trigger, + .open = simple_open, + .llseek = default_llseek, +}; + /** * rdtgroup_pseudo_lock_create - Create a pseudo-locked region * @rdtgrp: resource group to which pseudo-lock region belongs @@ -1385,10 +1422,14 @@ int rdtgroup_pseudo_lock_create(struct rdtgroup *rdtgrp) if (!IS_ERR_OR_NULL(debugfs_resctrl)) { plr->debugfs_dir = debugfs_create_dir(rdtgrp->kn->name, debugfs_resctrl); - if (!IS_ERR_OR_NULL(plr->debugfs_dir)) + if (!IS_ERR_OR_NULL(plr->debugfs_dir)) { debugfs_create_file("pseudo_lock_measure", 0200, plr->debugfs_dir, rdtgrp, &pseudo_measure_fops); + debugfs_create_file("pseudo_lock_restore", 0200, + plr->debugfs_dir, rdtgrp, + &pseudo_restore_fops); + } } dev = device_create(pseudo_lock_class, NULL, -- 2.17.0
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