There is currently no easy and architecture-independent way to find the
lowest unusable virtual address available to a process without
brute-force calculation. This patch allows a user to easily retrieve
this value via /proc/<pid>/status.
Using this patch, any program that previously needed to waste cpu cycles
recalculating a non-sensitive process-dependent value already known to
the kernel can now be optimized to use this mechanism.
Signed-off-by: Joel Savitz <jsavitz@xxxxxxxxxx>
---
Documentation/filesystems/proc.txt | 2 ++
fs/proc/task_mmu.c | 2 ++
2 files changed, 4 insertions(+)
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 66cad5c86171..1c6a912e3975 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -187,6 +187,7 @@ read the file /proc/PID/status:
VmLib: 1412 kB
VmPTE: 20 kb
VmSwap: 0 kB
+ VmTaskSize: 137438953468 kB
HugetlbPages: 0 kB
CoreDumping: 0
THP_enabled: 1
@@ -263,6 +264,7 @@ Table 1-2: Contents of the status files (as of 4.19)
VmPTE size of page table entries
VmSwap amount of swap used by anonymous private data
(shmem swap usage is not included)
+ VmTaskSize lowest unusable address in process virtual memory
HugetlbPages size of hugetlb memory portions
CoreDumping process's memory is currently being dumped
(killing the process may lead to a corrupted core)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 95ca1fe7283c..0af7081f7b19 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -74,6 +74,8 @@ void task_mem(struct seq_file *m, struct mm_struct *mm)
seq_put_decimal_ull_width(m,
" kB\nVmPTE:\t", mm_pgtables_bytes(mm) >> 10, 8);
SEQ_PUT_DEC(" kB\nVmSwap:\t", swap);
+ seq_put_decimal_ull_width(m,
+ " kB\nVmTaskSize:\t", mm->task_size >> 10, 8);
seq_puts(m, " kB\n");
hugetlb_report_usage(m, mm);
}
--
2.18.1
