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Date: Tue, 05 Jul 2022 18:44:53 -0400 From: Steven Rostedt <rostedt@...dmis.org> To: linux-kernel@...r.kernel.org Cc: Ingo Molnar <mingo@...nel.org>, Andrew Morton <akpm@...ux-foundation.org> Subject: [PATCH 00/13] tracing/events: Add __vstring and __assign_vstr helpers There's several places that open code the following logic: TP_STRUCT__entry(__dynamic_array(char, msg, MSG_MAX)), TP_fast_assign(vsnprintf(__get_str(msg), MSG_MAX, vaf->fmt, *vaf->va);) To load a string created by variable array va_list. The main issue with this approach is that "MSG_MAX" usage in the __dynamic_array() portion. That actually just reserves the MSG_MAX in the event, and even wastes space because there's dynamic meta data also saved in the event to denote the offset and size of the dynamic array. It would have been better to just use a static __array() field. Instead, create __vstring() and __assign_vstr() that work like __string and __assign_str() but instead of taking a destination string to copy, take a format string and a va_list pointer and fill in the values. It uses the helper: #define __trace_event_vstr_len(fmt, va) \ ({ \ va_list __ap; \ int __ret; \ \ va_copy(__ap, *(va)); \ __ret = vsnprintf(NULL, 0, fmt, __ap); \ va_end(__ap); \ \ min(__ret, TRACE_EVENT_STR_MAX); \ }) To figure out the length to store the string. It may be slightly slower as it needs to run the vsnprintf() twice, but it now saves space on the ring buffer, and more importantly, simplifies the code! Steven Rostedt (Google) (13): tracing/events: Add __vstring() and __assign_vstr() helper macros tracing/IB/hfi1: Use the new __vstring() helper tracing/ath: Use the new __vstring() helper tracing/brcm: Use the new __vstring() helper tracing/iwlwifi: Use the new __vstring() helper usb: chipidea: tracing: Use the new __vstring() helper xhci: tracing: Use the new __vstring() helper USB: mtu3: tracing: Use the new __vstring() helper usb: musb: tracing: Use the new __vstring() helper scsi: iscsi: tracing: Use the new __vstring() helper scsi: qla2xxx: tracing: Use the new __vstring() helper batman-adv: tracing: Use the new __vstring() helper mac80211: tracing: Use the new __vstring() helper ---- drivers/infiniband/hw/hfi1/trace_dbg.h | 8 ++------ drivers/net/wireless/ath/ath10k/trace.h | 14 ++++---------- drivers/net/wireless/ath/ath11k/trace.h | 7 ++----- drivers/net/wireless/ath/ath6kl/trace.h | 14 ++++---------- drivers/net/wireless/ath/trace.h | 7 ++----- drivers/net/wireless/ath/wil6210/trace.h | 7 ++----- .../wireless/broadcom/brcm80211/brcmfmac/tracepoint.h | 12 ++++-------- .../brcm80211/brcmsmac/brcms_trace_brcmsmac_msg.h | 12 ++++-------- drivers/net/wireless/intel/iwlwifi/iwl-devtrace-msg.h | 12 ++++-------- drivers/usb/chipidea/trace.h | 4 ++-- drivers/usb/host/xhci-trace.h | 4 ++-- drivers/usb/mtu3/mtu3_trace.h | 4 ++-- drivers/usb/musb/musb_trace.h | 4 ++-- include/linux/trace_events.h | 18 ++++++++++++++++++ include/trace/events/iscsi.h | 4 ++-- include/trace/events/qla.h | 4 ++-- include/trace/stages/stage1_struct_define.h | 3 +++ include/trace/stages/stage2_data_offsets.h | 3 +++ include/trace/stages/stage4_event_fields.h | 3 +++ include/trace/stages/stage5_get_offsets.h | 4 ++++ include/trace/stages/stage6_event_callback.h | 7 +++++++ net/batman-adv/trace.h | 7 ++----- net/mac80211/trace_msg.h | 6 ++---- 23 files changed, 82 insertions(+), 86 deletions(-)
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